Effect of parathyroid hormone on transport by toad and turtle bladder

1987 ◽  
Vol 252 (1) ◽  
pp. R63-R68
Author(s):  
S. Sabatini ◽  
N. A. Kurtzman
Keyword(s):  
Parathyroid Hormone ◽  
Epithelial Cells ◽  
Calcium Uptake ◽  
Short Circuit ◽  
Calcium Ionophore ◽  
Toad Bladder ◽  
Base Line ◽  
Ionophore A23187 ◽  
45Ca Uptake ◽  
Turtle Bladder

We recently demonstrated that parathyroid hormone (PTH) inhibited both vasopressin- and cyclic AMP-stimulated water transport in the toad bladder. This was associated with an increase in calcium uptake by isolated epithelial cells. We postulated that PTH exerts its action on H2O transport by directly stimulating calcium uptake. The current study was designed to compare the effects of PTH and the calcium ionophore, A23187, on H2O and Na transport and H+ secretion in toad and turtle bladders. In toad bladder, PTH and A23187 decreased arginine vasopressin (AVP)-stimulated H2O flow and short-circuit current (SCC) after 60 min serosal incubation. In turtle bladder A23187 decreased SCC to 79.3 +/- 3.6% of base line (P less than 0.05), and significantly decreased RSCC as well. PTH had no effect on SCC or H+ secretion in turtle bladders. Both PTH and A23187 increased 45Ca uptake in toad bladder epithelial cells; only A23187 increased 45Ca uptake in the turtle bladder. The different action of PTH in these two membranes, compared with that of the calcium ionophore, illustrates the selectivity of PTH on membrane transport. PTH increases calcium uptake and decreases transport only in a hormone-sensitive epithelium, whereas the ionophore works in virtually all living membranes. The mode of action of these two agents to increase calcium uptake is, therefore, likely different.

Cholinergic modulation of water transport in the toad bladder

1980 ◽  
Vol 239 (2) ◽  
pp. F154-F159
Author(s):  
J. A. Arruda ◽  
S. Sabatini
Keyword(s):  
Cyclic Amp ◽  
Muscarinic Receptor ◽  
Water Transport ◽  
Water Flow ◽  
Calcium Uptake ◽  
Toad Bladder ◽  
Base Line ◽  
Cholinergic Modulation ◽  
45Ca Uptake ◽  
A 23187

The effect of carbachol on water transport by the toad bladder was studied. Carbachol caused a small increase in base-line water flow and inhibited, partially, vasopressin- (AVP) or cyclic AMP-stimulated water flow. The effect of carbachol on base-line or AVP-stimulated water flow was totally prevented by atropine, indicating that the effect of cabachol on water transport is mediated through a muscarinic receptor. Carbachol caused a significant increase in 45Ca uptake by toad bladder; this increase in calcium uptake could be prevented by atropine, pentobarbital, or lanthanum. The effect of carbachol on base-line and AVP-stimulated water flow was also prevented by pentobarbital or lanthanum, suggesting that the effect of carbachol is mediated, at least in part, by an increase in calcium uptake. The ionophore A-23187, an agent that increased 45Ca uptake, also enhanced base-line water flow and inhibited AVP-stimulated water flow. The effects of carbachol and the ionophore A-23187 on base-line water flow, AVP-stimulated water flow, and on calcium uptake were not additive, suggesting that both agents alter water transport by a similar mechanism. These data demonstrate that carbachol stimulates base-line water transport and inhibits AVP-stimulated water transport. They suggest that the alteration in water transport induced by carbachol is related to an increase in calcium uptake.

Aldosterone-stimulated transmethylations are linked to sodium transport

1985 ◽  
Vol 248 (1) ◽  
pp. F43-F47 ◽  
Author(s):  
W. P. Wiesmann ◽  
J. P. Johnson ◽  
G. A. Miura ◽  
P. K. Chaing
Keyword(s):  
Epithelial Cells ◽  
Sodium Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Toad Bladder ◽  
Methylation Inhibitor ◽  
In Cells

The effect of aldosterone (Aldo) on phospholipid (PL) biosynthesis in cultured toad bladder epithelial cells was studied in cells incubated with [1,2-14C]choline and [methyl-3H]methionine over a 5-h period. Aldo (10(-7) M) did not alter the uptake of either precursor but significantly stimulated the incorporation of both labels into phosphatidylcholine (PC), the only PL labeled. 3H labeling of PC increased 29% and 14C incorporation into PC increased 34% in cells exposed to Aldo. A similar 30% increase in protein carboxymethylation occurred in cells treated with Aldo. 3-Deazaadenosine (DZA), a methylation inhibitor, abolished the Aldo-stimulated increase in PC labeling from [3H]methionine. PC labeling from [1,2-14C]choline was not affected by DZA. Basal and Aldo-stimulated protein carboxy-methylation were inhibited by DZA. DZA (300 microM) caused a mild decrease in basal short-circuit current (ISC) but completely inhibited the ISC response to 10(-7) M Aldo. Inhibition was complete when DZA was added up to 2 h following exposure to Aldo, and was reversible. Cells previously exposed to Aldo showed a significant increase in ISC within 2 h following removal of DZA. We conclude that Aldo stimulates PL methylation, protein carboxymethylation, and turnover of PC from choline. Inhibition of methylation reactions coincides with the inhibition of ISC response to Aldo.

Evidence for separate cellular origins of sodium and acid-base transport in the turtle bladder

1986 ◽  
Vol 250 (4) ◽  
pp. C609-C616 ◽  
Author(s):  
J. H. Durham ◽  
W. Nagel
Keyword(s):  
Epithelial Cells ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Transport Processes ◽  
Electrical Parameters ◽  
Acid Base ◽  
Intracellular Potential ◽  
Turtle Bladder ◽  
Stimulation Of

Transmembrane electrical parameters of the epithelial cells in short-circuited turtle bladders were measured to determine whether those cells participating in Na reabsorption also participate in electrogenic transepithelial acidification and alkalinization. Amiloride-induced increases in intracellular potential (Vsca), apical fractional resistance (FRa), and concomitant decreases in short-circuit current (Isc) denote the participation of the impaled cells in Na reabsorption. In bladders from postabsorptive turtles, amiloride increased Vsca by -45 mV, increased FRa by 37%, and decreased Isc from 36 to -10 microA/cm2. In bladders from NaHCO3-loaded turtles, amiloride increased Vsca by -21 mV, FRa by 21%, and decreased Isc from 22 to 0 microA/cm2. Neither the subsequent inhibition of the negative acidification current in postabsorptive bladders, nor stimulation of positive alkalinization current in bladders from NaHCO3-loaded turtles was associated with any transmembrane electrical change that could be attributed to changes in those transport processes. It is concluded that the electrogenic luminal acidification and alkalinization processes of the turtle bladder are not produced by, or electrically coupled to, those cells that are involved in Na reabsorption.

31P nuclear magnetic resonance analysis of frog skin

1982 ◽  
Vol 243 (1) ◽  
pp. C74-C80 ◽  
Author(s):  
L. E. Lin ◽  
M. Shporer ◽  
M. M. Civan
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Epithelial Cells ◽  
Inorganic Phosphate ◽  
Frog Skin ◽  
Short Circuit ◽  
Toad Bladder ◽  
Nuclear Magnetic Resonance Analysis ◽  
31P Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

The intracellular phosphate composition of whole and split frog skins has been studied by 31P nuclear magnetic resonance (NMR) analysis. The spectra were similar to those previously recorded from isolated epithelial cells of toad bladder. However, qualitative differences were noted in comparison with spectra from whole toad bladder. The 31P spectra from whole frog skin reflect the intracellular compositions of the epithelial cells, whereas subepithelial elements contribute significantly to the total observed 31P signals from toad bladder. Analyzed at 4 degrees C, the average phosphocreatine (PCr) and ATP concentrations of frog skin are of similar magnitude. The ratio of [PCr] to [ATP + ADP] depends on time, tissue oxygen tension, temperature, and extracellular inorganic phosphate concentration. Both this ratio and the short-circuit current (measured in parallel experiments) fell during the course of aerating frog skins in Ringer solution at room temperature. The intracellular inorganic phosphate (Pi) signal was identified. After reduction of extracellular pH, the signal did not shift immediately but subsequently did undergo an acid shift.

scholarly journals Calcium uptake and release by isolated cortices and microsomes from the unfertilized egg of the sea urchin Strongylocentrotus droebachiensis.

1986 ◽  
Vol 102 (6) ◽  
pp. 2205-2210 ◽  
Author(s):  
J A Oberdorf ◽  
J F Head ◽  
B Kaminer
Keyword(s):  
Sea Urchin ◽  
Calcium Uptake ◽  
Inositol Trisphosphate ◽  
Calcium Ionophore ◽  
Strongylocentrotus Droebachiensis ◽  
Cortical Granule ◽  
Free Calcium ◽  
Cortical Region ◽  
Ionophore A23187 ◽  
Dependent Manner

Isolated cortices from unfertilized sea urchin eggs sequester calcium in an ATP-dependent manner when incubated in a medium containing free calcium levels characteristic of the resting cell (approximately 0.1 microM). This ATP-dependent calcium uptake activity was measured in the presence of 5 mM Na azide to prevent mitochondrial accumulation, was increased by oxalate, and was blocked by 150 microM quercetin and 50 microM vanadate (known inhibitors of calcium uptake into the sarcoplasmic reticulum). Cortical regions preloaded with 45Ca in the presence of ATP were shown to dramatically increase their rate of calcium efflux upon the addition of (a) the calcium ionophore A23187 (10 microM), (b) trifluoperazine (200 microM), (c) concentrations of free calcium that activated cortical granule exocytosis, and (d) the calcium mobilizing agent inositol trisphosphate. This pool of calcium is most likely sequestered in the portion of the egg's endoplasmic reticulum that remains associated with the cortical region during its isolation. We have developed a method for obtaining a high yield of purified microsomal vesicles from whole eggs. This preparation also demonstrates ATP-dependent calcium sequestering activity which increases in the presence of oxalate and has similar sensitivities to calcium transport inhibitors; however, the isolated microsomal vesicles did not show any detectable release of calcium when exposed to inositol trisphosphate.

EVIDENCE FOR A NOVEL INHIBITION OF CALCIUM UPTAKE INTO CHICK BONE IN RESPONSE TO BOVINE PARATHYROID HORMONE (1-34) OR 16, 16-DIMETHYL PROSTAGLANDIN E2 IN VIVO

1985 ◽  
Vol 105 (3) ◽  
pp. R5-R8 ◽  
Author(s):  
A.J. Shaw ◽  
C.G. Dacke
Keyword(s):  
Parathyroid Hormone ◽  
Soft Tissue ◽  
Calcium Uptake ◽  
Separate Experiment ◽  
Response Curves ◽  
45Ca Uptake ◽  
Microwave Fixation ◽  
Absolute Basis ◽  
Bovine Parathyroid Hormone

ABSTRACT Mechanisms of initial hypercalcaemic responses to parathyroid hormone (PTH) and 16, 16-dimethyl prostaglandin (PG) E2 have been investigated in 10-to 12-day-old chicks in vivo using a combination of acute 45Ca injection and microwave fixation to stabilize tissue isotope levels. Single i.v. injection of 16, 16-dimethyl PGE2 (20 μg/100 g body wt) caused an approximately 100% increase in soft tissue 45Ca levels compared with vehicle control injected chicks at 30 min. 45Ca levels were lowered in calvarium by 26% and in femur by 60% with this treatment. Bovine PTH (1-34) (3.3 μg/100 g body wt) had no effect on soft tissue 45Ca levels, but in calvarium it had a similar effect to the PG. In femur this dose of PTH lowered 45Ca by 19%. When expressed on an absolute basis (c.p.m./ 100 mg tissue wt), responses to the PG in soft tissue were only 3 and 10% respectively of those in femur and calvarium. The duration of inhibitory responses in bone were examined and those to PTH found to be transient (< 45 min) compared with the responses to the PG (> 135 min). Dose-response curves for PTH- and PG-induced inhibition of 45Ca uptake into femur at 15 min were essentially parallel and indicated that the lowest doses of PTH and PG used (0.74 μg and 1.1 μg/100 body wt respectively) produced significant responses. In a separate experiment it was found that inhibition of 45Ca uptake into femur was evident as early as 3 min following PTH or PG injection. The experiments described in this paper collectively indicate a higherto unrecognized action of PTH and PGE in the regulation of Ca metabolism in chicks which is to inhibit entry of Ca into bone.

scholarly journals THE EFFECT OF CALCIUM WITHDRAWAL ON THE STRUCTURE AND FUNCTION OF THE TOAD BLADDER

1965 ◽  
Vol 25 (3) ◽  
pp. 195-209 ◽  
Author(s):  
Richard M. Hays ◽  
Bayla Singer ◽  
Sasha Malamed
Keyword(s):  
Epithelial Cells ◽  
Sodium Transport ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Structure And Function ◽  
Toad Bladder ◽  
Active Sodium ◽  
Bathing Medium ◽  
Active Sodium Transport ◽  
And Function

Previous reports have indicated that calcium is necessary to support active sodium transport by the toad bladder, and may be required as well in the action of vasopressin on both toad bladder and frog skin. The structure and function of the toad bladder has been studied in the absence of calcium, and a reinterpretation of the previous findings now appears possible. When calcium is withdrawn from the bathing medium, epithelial cells detach from one another and eventually from their supporting tissue. The short-circuit current (the conventional means of determining active sodium transport) falls to zero, and vasopressin fails to exert its usual effect on short-circuit current and water permeability. However, employing an indirect method for the estimation of sodium transport (oxygen consumption), it is possible to show that vasopressin exerts its usual effect on Qoo2 when sodium is present in the bathing medium. Hence, it appears that the epithelial cells maintain active sodium transport when calcium is rigorously excluded from the bathing medium, and continue to respond to vasopressin. The failure of conventional techniques to show this can be attributed to the structural alterations in the epithelial layer in the absence of calcium. These findings may provide a model for the physiologic action of calcium in epithelia such as the renal tubule.

scholarly journals Signaling in TRPV1-induced platelet activating factor (PAF) in human esophageal epithelial cells

2010 ◽  
Vol 298 (2) ◽  
pp. G233-G240 ◽  
Author(s):  
Jie Ma ◽  
Karen M. Harnett ◽  
Jose Behar ◽  
Piero Biancani ◽  
Weibiao Cao
Keyword(s):  
Epithelial Cells ◽  
Western Blot ◽  
Transient Receptor Potential ◽  
Platelet Activating Factor ◽  
Calcium Ionophore ◽  
Transferase Activity ◽  
Ionophore A23187 ◽  
Acetyl Coa ◽  
Coa Transferase

Transient receptor potential channel, vanilloid subfamily member 1 (TRPV1) receptors were identified in human esophageal squamous epithelial cell line HET-1A by RT-PCR and by Western blot. In fura-2 AM-loaded cells, the TRPV1 agonist capsaicin caused a fourfold cytosolic calcium increase, supporting a role of TRPV1 as a capsaicin-activated cation channel. Capsaicin increased production of platelet activating factor (PAF), an important inflammatory mediator that acts as a chemoattractant and activator of immune cells. The increase was reduced by the p38 MAP kinase (p38) inhibitor SB203580, by the cytosolic phospholipase A2 (cPLA2) inhibitor AACOCF3, and by the lyso-PAF acetyltransferase inhibitor sanguinarin, indicating that capsaicin-induced PAF production may be mediated by activation of cPLA2, p38, and lyso-PAF acetyltransferase. To establish a sequential signaling pathway, we examined the phosphorylation of p38 and cPLA2 by Western blot. Capsaicin induced phosphorylation of p38 and cPLA2. Capsaicin-induced p38 phosphorylation was not affected by AACOCF3. Conversely, capsaicin-induced cPLA2 phosphorylation was blocked by SB203580, indicating that capsaicin-induced PAF production depends on sequential activation of p38 and cPLA2. To investigate how p38 phosphorylation may result from TRPV1-mediated calcium influx, we examined a possible role of calmodulin kinase (CaM-K). p38 phosphorylation was stimulated by the calcium ionophore A23187 and by capsaicin, and the response to both agonists was reduced by a CaM inhibitor and by CaM-KII inhibitors, indicating that calcium induced activation of CaM and CaM-KII results in P38 phosphorylation. Acetyl-CoA transferase activity increased in response to capsaicin and was inhibited by SB203580, indicating that p38 phosphorylation in turn causes activation of acetyl-CoA transferase to produce PAF. Thus epithelial cells produce PAF in response to TRPV1-mediated calcium elevation.

Calcium transport, Ca2(+)-ATPase, and lipid order in rabbit ocular lens membranes

1991 ◽  
Vol 260 (4) ◽  
pp. C731-C737 ◽  
Author(s):  
N. A. Delamere ◽  
C. A. Paterson ◽  
D. Borchman ◽  
K. L. King ◽  
S. A. Cawood
Keyword(s):  
Atpase Activity ◽  
Temperature Dependence ◽  
Calcium Transport ◽  
Calcium Uptake ◽  
Calcium Ionophore ◽  
Membrane Vesicles ◽  
Lipid Phase ◽  
Ionophore A23187 ◽  
Lipid Order ◽  
Uptake Process

Calcium transport was monitored by measuring ATP-dependent 45Ca uptake into membrane vesicles prepared from rabbit lens cortex. Calcium-stimulated adenosinetriphosphatase (Ca2(+)-ATPase) activity was also measured in the same membrane preparation. Both uptake and Ca2(+)-ATPase activity were inhibited by vanadate. Calcium activation of the uptake process was similar to that of the Ca2(+)-ATPase. Calcium uptake was prevented by calcium ionophore A23187, suggesting that the calcium transported into the vesicles remains diffusible. The ATP-dependent calcium uptake probably represents the transport of calcium into “inside-out” membrane vesicles by the Ca2(+)-ATPase mechanism that normally shifts calcium outward from the lens cytoplasm. The temperature dependence of the Ca2(+)-ATPase and the calcium uptake process was determined. Because lipid order can influence Ca2(+)-ATPase function, we attempted to correlate calcium transport with the physical state of the membrane lipids. Infrared spectroscopy was used to determine the temperature dependence of the CH2 symmetric stretching frequency (an order parameter) in the lipids. A similarity was noted between the temperature-dependence curves for lipid order, Ca2(+)-ATPase, and calcium uptake rate. Entropy, enthalpy, and transition temperature calculated for the Ca2(+)-ATPase and calcium uptake process were in the same range as those parameters calculated for the lipid-phase transition.

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