Active calcium transport in the skin of the frog Rana pipiens: kinetics and seasonal rhythms.

1995 ◽  
Vol 198 (4) ◽  
pp. 967-974
Author(s):  
D F Stiffler
Keyword(s):  
Calcium Transport ◽  
Rana Pipiens ◽  
Dorsal Skin ◽  
Electrochemical Gradient ◽  
Fish Gill ◽  
Seasonal Rhythms ◽  
Active Calcium ◽  
Net Flux ◽  
Ventral Skin ◽  
Freshwater Environments

The frog Rana pipiens takes up Ca2+ against an electrochemical gradient from dilute external solutions that are similar to natural freshwater environments. The influx is dependent upon external [Ca2+] and is saturable. Kinetic analysis yielded a Km of 0.625 mmol l-1 and a Jmax of 38 nmol cm-2h-1. These kinetic variables suggest that both the affinity and capacity are smaller than those for Na+ and Cl- transport in the skin of the same species. They are also smaller than those for Ca2+ transport in fish gill. A significant portion (20-25%) of the Ca2+ entering a frog remains in Ca(2+)-rich layers of the skin, with ventral skin containing about three times as much Ca2+ as dorsal skin. There are seasonal rhythms in Ca2+ exchange: although Ca2+ influx does not vary significantly over the year, efflux is minimal in July, while net flux, which is negative most of the year, appears to be positive in July. Since these fluxes do not include dietary calcium, one cannot conclude that feeding frogs are in negative Ca2+ balance.

scholarly journals Calcium Absorption by the Midgut of the Blowfly, Calliphora Vicina

1985 ◽  
Vol 114 (1) ◽  
pp. 551-561 ◽  
Author(s):  
Colin W. Taylor
Keyword(s):  
Calcium Transport ◽  
Calcium Absorption ◽  
Water Flux ◽  
Calcium Flux ◽  
Calliphora Vicina ◽  
Internal Perfusion ◽  
Electrochemical Gradient ◽  
Saturation Kinetics ◽  
Active Calcium ◽  
Net Water Flux

The isolated midgut of the adult blowfly, Calliphora vicina, can be maintained under internal perfusion for over 6h, and calcium absorption measured by including 45Ca in the perfusing saline with [3H[inulin as a volume marker. The midgut has a considerable capacity to transport calcium from the lumen (L) to the bathing saline (BS) against its electrochemical gradient and in the absence of an appreciable net water flux across the gut. Calcium absorption (L-BS) shows saturation kinetics, is totally and reversibly inhibited by metabolic poisons and is accompanied by a negligible backflux (BS-L). It is concluded that the midgut of C. vicina is capable of active calcium transport and that the entire transepithelial calcium flux occurs via a transcellular route. This contrasts with the mammalian duodenum, where absorption occurs via a combination of transcellular and paracellular routes.

A new species of Phrynopus from Departamento Cusco, southern Peru(Anura: Brachycephalidae)

Zootaxa ◽  
2007 ◽  
Vol 1618 (1) ◽  
pp. 61-68 ◽  
Author(s):  
JUAN C. CHAPARRO ◽  
IGNACIO DE LA RIVA ◽  
JOSÉ M. PADIAL ◽  
JOSÉ A. OCHOA ◽  
EDGAR LEHR
Keyword(s):  
New Species ◽  
Tympanic Membrane ◽  
Cloud Forest ◽  
Medium Size ◽  
Dorsal Skin ◽  
Southern Peru ◽  
Upper Limits ◽  
Ventral Skin ◽  
A New Species

We describe a new species of Phrynopus (Anura: Brachycephalidae) from two close localities at the upper limits of cloud forest in the southern Peruvian Departamento Cusco, between 3555–3950 m a.s.l. The new species is characterized by having medium size (maximum snout-vent length 23.4 mm), dentigerous processes of vomers absent, tympanic membrane inconspicuous, dorsal skin coarsely shagreen in life, dorsolateral folds, ventral skin areolate, dorsum tan, venter bold black with conspicuous bluish-gray spots, and a bluish-white iris.

CaBPr facilitates intracellular diffusion for Ca pumping in distal convoluted tubule

1988 ◽  
Vol 255 (3) ◽  
pp. F558-F562 ◽  
Author(s):  
F. Bronner ◽  
W. D. Stein
Keyword(s):  
Vitamin D ◽  
Calcium Binding ◽  
Distal Convoluted Tubule ◽  
Ion Concentration ◽  
Electrochemical Gradient ◽  
Active Vitamin ◽  
Animal Data ◽  
Intracellular Diffusion ◽  
Intracellular Ca ◽  
Active Calcium

The system of renal Ca transport in the rat is modeled in terms of two classes of processes: a nonsaturable flux that predominates in the proximal tubule, and an active, vitamin D-dependent flux with major expression in the distal convoluted tubule. There transport is against an electrochemical gradient, with much of the efflux probably mediated by the Ca/Mg-ATPase. Calculations of the rate of free Ca diffusion in tubular cells indicate that an unaided flux would be only one-seventy-seventh of that found experimentally. It is suggested that the vitamin D-induced renal calcium binding protein, CaBPr, Mr approximately 28,000, in raising total cellular calcium by three orders of magnitude, increases the transcellular Ca flux and thus the free intracellular Ca ion concentration at the basolateral pole, allowing the Ca/Mg-ATPase to function near its maximum. Analysis of the rate of nonsaturable Ca flux throughout the kidney tubule suggests a paracellular pathway via bulk flow, following water that is driven osmotically. Evaluation of whole animal data in terms of these two classes of calcium fluxes indicates that our model is consistent with experimental observations and assigns a functional role to active calcium transport.

Influence of ATP on sarcoplasmic reticulum function of vascular smooth muscle

1982 ◽  
Vol 242 (3) ◽  
pp. C242-C249 ◽  
Author(s):  
G. D. Ford ◽  
M. L. Hess
Keyword(s):  
Smooth Muscle ◽  
Sarcoplasmic Reticulum ◽  
Vascular Smooth Muscle ◽  
Calcium Transport ◽  
Calcium Uptake ◽  
Specific Activity ◽  
Substrate Inhibition ◽  
Uptake Activity ◽  
Active Calcium ◽  
Active Preparation

A vesicular fraction isolated from bovine aorta and enriched in fragmented sarcoplasmic reticulum (FSR) exhibited active calcium transport and ATPase activity. By use of a hypotonic NaHCO3 extraction solution, an active preparation was isolated that retained activity for up to 4 days. A small but significant (P less than 0.05) Ca2+-stimulated, Mg2+-dependent ATPase associated with calcium transport was demonstrated with a specific activity of 0.33 mumol inorganic phosphate (Pi).mg-1.min-1. The basal Mg2+ ATPase demonstrated Michaelis-Menten kinetics [Km(Mg2+-ATP) = 0.44 +/- 0.01 X 10(-3) M; Vmax = 2.22 +/- 0.01 mumolPi.mg-1.min-1]. The Ca2+-stimulated, Mg2+-ATPase demonstrated apparent substrate inhibition (Ks approximately 10 mM) with no evidence for end-product (ADP) or excess added Ca2+ contributing to this inhibition. Oxalate-supported active calcium uptake velocities also exhibited quantitatively similar substrate inhibition. These results suggest that FSR from vascular smooth muscle contains either two enzymes or one enzyme with two isomeric forms, one of which is associated with the calcium uptake activity of this structure and the other of unknown function.

scholarly journals Investigation of the Accompaniment of Calcium During Active Calcium Transport from Human Erythrocyte Ghosts

1974 ◽  
Vol 63 (5) ◽  
pp. 590-600 ◽  
Author(s):  
Erik J. Olson ◽  
Ralph J. Cazort
Keyword(s):  
Cell Membrane ◽  
Calcium Transport ◽  
Inorganic Phosphate ◽  
Adenine Nucleotide ◽  
Erythrocyte Ghosts ◽  
High Dilutions ◽  
A Cell ◽  
Active Calcium ◽  
Phosphate Analysis ◽  
Almost All

To determine whether a cell metabolite was involved in active calcium transport, the cell contents of human erythrocytes were subjected to high dilutions and the resultant ghosts were checked for their ability to actively transport calcium. It was found that the diluted erythrocyte ghosts did retain their capacity to actively transport calcium and that the characteristics of this transport process appeared to be unaltered by the high dilutions. Calcium analysis of the cell membrane and cell supernatant indicated that almost all of the calcium was lost from the cell solution rather than the cell membrane as active calcium transport proceeded. Therefore it appeared that calcium was able to cross the cell membrane without the aid of a cell metabolite. Investigations with layered erythrocytes indicated that the active transport of calcium was not assisted by centrifugation. Neither inorganic phosphate, pyrophosphate, nor an adenine nucleotide appeared to accompany calcium across the membrane as indicated by total phosphate and inorganic phosphate analysis and 260-nm readings of the deproteinized supernatant.

Active Calcium Transport by Porcine Thyroid Microsomes*

Endocrinology ◽  
1986 ◽  
Vol 119 (5) ◽  
pp. 2058-2065 ◽  
Author(s):  
YOICHI NAKAMURA ◽  
TAKASHI MIYAMOTO ◽  
MASASHI KOONO ◽  
SACHIYA OHTAKI
Keyword(s):  
Calcium Transport ◽  
Active Calcium

scholarly journals Analysis of 1,25-Dihydroxyvitamin D3 Genomic Action Reveals Calcium-Regulating and Calcium-Independent Effects in Mouse Intestine and Human Enteroids

2020 ◽  
Vol 41 (1) ◽  
pp. e00372-20
Author(s):  
Shanshan Li ◽  
Jessica De La Cruz ◽  
Steven Hutchens ◽  
Somshuvra Mukhopadhyay ◽  
Zachary K. Criss ◽  
...  
Keyword(s):  
Vitamin D ◽  
Calcium Transport ◽  
Target Genes ◽  
Dihydroxyvitamin D3 ◽  
Transgenic Expression ◽  
Distal Intestine ◽  
Dihydroxyvitamin D ◽  
Active Calcium ◽  
Independent Effects ◽  
Proximal Intestine

ABSTRACTAlthough vitamin D is critical for the function of the intestine, most studies have focused on the duodenum. We show that transgenic expression of the vitamin D receptor (VDR) only in the distal intestine of VDR null mice (KO/TG mice) results in the normalization of serum calcium and rescue of rickets. Although it had been suggested that calcium transport in the distal intestine involves a paracellular process, we found that the 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]-activated genes in the proximal intestine associated with active calcium transport (Trpv6, S100g, and Atp2b1) are also induced by 1,25(OH)2D3 in the distal intestine of KO/TG mice. In addition, Slc30a10, encoding a manganese efflux transporter, was one of the genes most induced by 1,25(OH)2D3 in both proximal and distal intestine. Both villus and crypt were found to express Vdr and VDR target genes. RNA sequence (RNA-seq) analysis of human enteroids indicated that the effects of 1,25(OH)2D3 observed in mice are conserved in humans. Using Slc30a10−/− mice, a loss of cortical bone and a marked decrease in S100g and Trpv6 in the intestine was observed. Our findings suggest an interrelationship between vitamin D and intestinal Mn efflux and indicate the importance of distal intestinal segments to vitamin D action.

Effects of pH on apical calcium entry and active calcium transport in rabbit cortical collecting system

1994 ◽  
Vol 266 (4) ◽  
pp. F620-F627 ◽  
Author(s):  
R. J. Bindels ◽  
A. Hartog ◽  
S. L. Abrahamse ◽  
C. H. Van Os
Keyword(s):  
Calcium Transport ◽  
Apical Membrane ◽  
Channel Blockers ◽  
Intracellular Acidification ◽  
Apical Side ◽  
Collecting Ducts ◽  
Effects Of Ph ◽  
Active Calcium ◽  
Permeable Supports ◽  
Collecting System

Rabbit connecting tubules and cortical collecting ducts were isolated by immunodissection and cultured on permeable supports. The monolayers actively transported Ca2+ with a net transcellular rate of 92 +/- 3 nmol.h-1.cm-2. Methoxyverapamil, felodipine, diltiazem, omega-conotoxin GVIA, and omega-agatoxin IVA when added to the apical side had no effect on Ca2+ absorption. Neither hyperpolarization nor depolarization of the apical membrane affected Ca2+ transport rates significantly. Stepwise lowering of the apical pH (pHa) from 8.0 to 5.6 gradually inhibited Ca2+ transport from 88 +/- 5 to 7 +/- 2 nmol.h-1.cm-2. Measuring the intracellular pH (pHi) with 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein revealed that lowering the pHa from 8.0 to 5.6 decreased pHi from 7.8 to 6.7. To determine whether inhibition of Ca2+ absorption results from intracellular acidification, pHi was lowered using an NH4Cl pulse while extracellular pH was kept constant. Intracellular acidification from 7.4 +/- 0.2 to 6.9 +/- 0.1 reduced Ca2+ absorption by 26 +/- 6% only. In addition, lowering of the basolateral pH to 6.2 resulted in a pHi of 6.8 +/- 0.1, without affecting Ca2+ absorption rates. In conclusion, the basal Ca2+ influx mechanism in the apical membrane is most likely a voltage-independent Ca2+ transporter, insensitive to Ca2+ channel blockers, but strongly inhibited by apical acidification.

Sign in / Sign up

Export Citation Format

Share Document