Studies on the mechanism of fluid secretion by isolated salivary glands of Calliphora

1976 ◽  
Vol 64 (2) ◽  
pp. 311-322
Author(s):  
M. J. Berridge ◽  
B. D. Lindley ◽  
W. T. Prince
Keyword(s):  
Salivary Glands ◽  
Apical Membrane ◽  
Potassium Concentration ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Sodium Permeability ◽  
Bathing Medium ◽  
Major Cation ◽  
Diuretic Agent ◽  
External Potassium

1. Potassium is the major cation in the secretion of the salivary glands of Calliphora and is necessary for full secretory rates. 2. Other ions (rubidium and sodium) can support secretion in the absence of potassium. 39. During stimulation with 5-HT a Nernst plot of the basal membrane potential has a slope of 53 mV for a tenfold change in external potassium concentration and the slope at rest deviates from this over the range I-20 mM external potassium. 4. Hyperpolarization of the basal membrane by 5-HT is abolished if the chloride in the bathing medium is replaced by isethionate. 5. The diuretic agent amiloride inhibits fluid secretion by a mechanism which may include a reduction in calcium entry in addition to its recognized effect on sodium permeability. 6. A model is proposed in which fluid secretion is driven by the active transport of potassium across the apical membrane with chloride following passively.

scholarly journals Secretion by the Malpighian tubules of Rhodnius prolixus stal: electrical events

1984 ◽  
Vol 110 (1) ◽  
pp. 275-290 ◽  
Author(s):  
M. J. O'Donnell ◽  
S. H. Maddrell
Keyword(s):  
Apical Membrane ◽  
Electrical Response ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Chloride Permeability ◽  
Bathing Medium ◽  
Before And After ◽  
Electrical Gradient ◽  
Cation Pump

Transepithelial and intracellular potentials have been simultaneously recorded from Rhodnius upper Malpighian tubules before and after stimulation of fluid secretion. The transepithelial electrical response to the diuretic hormone mimic 5-hydroxytryptamine (5-HT) was triphasic; recordings of intracellular potential changes indicated that the three phases represented successive events at the apical membrane. Depolarizations produced by increasing the bathing medium potassium concentration indicated that the basal membrane was much more permeable to potassium than to sodium. Electrical responses to chloride-free saline were inconsistent with a significant basal membrane chloride permeability. Chloride movements across the basal membrane were opposed by an electrical gradient of about 65 mV. The results of experiments in which tubules were exposed to chloride-free saline or sodium-free saline suggested that chloride entry into the cells was linked to the entry of Na+ and K+. The effects of furosemide and bumetanide upon secretion and potential changes suggested that chloride crossed the basal membrane through co-transport with Na+ and K+. Chloride probably crosses the apical membrane into the lumen passively in response to a favourable electrical gradient of about 35 mV. Cations must be actively pumped into the lumen against an electrical gradient of 35 mV. Our results support previous evidence for an apical cation pump which actively transports Na and K into the lumen. A tentative model of ionic movements during fluid secretion is presented. It is suggested that the apical cation pump maintains sodium at low intracellular concentrations, thereby maintaining a favourable gradient for entry of Na+ through the proposed basal co-transport step. The suggested stoichiometry is Na+:K+:2 Cl-.

The Effects of 5-Hydroxytryptamine and Cyclic Amp on the Potential Profile across Isolated Salivary Glands

1972 ◽  
Vol 56 (2) ◽  
pp. 323-333
Author(s):  
WILLIAM T. PRINCE ◽  
MICHAEL J. BERRIDGE
Keyword(s):  
Salivary Gland ◽  
Membrane Potential ◽  
Cyclic Amp ◽  
Salivary Glands ◽  
Apical Membrane ◽  
Basal Membrane ◽  
Potential Profile ◽  
Step Potential ◽  
Bathing Medium ◽  
Transepithelial Potential

1. The sites of the transepithelial potential changes produced by 5-HT and cyclic AMP in the salivary gland of the blowfly (Calliphora) have been investigated. 2. Microelectrodes recorded a two-step potential profile across this epithelium. The cell was negative to both the bathing medium and the saliva. 3. The basal membrane potential was 44·0±0·2 mV and was affected very little by application of either 5-HT or cyclic AMP. 4. The apical membrane was depolarized by 5-HT and in contrast was hyperpolarized by cyclic AMP. 5. On the basis of these results it is concluded that 5-HT has two actions: (a) to stimulate a potassium pump on the apical membrane using cyclic AMP as an intermediary, (b) to increase chloride movement by a mechanism not directly involving cyclic AMP.

Long-term Adaptations of Sabella Giant Axons to Hyposmotic Stress

1978 ◽  
Vol 75 (1) ◽  
pp. 253-263
Author(s):  
J. E. TREHERNE ◽  
Y. PICHON
Keyword(s):  
Sea Water ◽  
Potassium Concentration ◽  
Resting Potential ◽  
Sodium Permeability ◽  
Bathing Medium ◽  
Appreciable Change ◽  
Axon Membrane ◽  
Giant Axons

Reprint requests should be addressed to Dr Treherne. Sabella is a euryhaline osmoconformer which is killed by direct transfer to 50% sea water, but can adapt to this salinity with progressive dilution of the sea water. The giant axons were adapted to progressive dilution of the bathing medium (both in vivo and in vitro) and were able to function at hyposmotic dilutions (down to 50%) sufficient to induce conduction block in unadapted axons. Hyposmotic adaptation of the giant axon involves a decrease in intracellular potassium concentration which tends to maintain a relatively constant resting potential during adaptation despite the reduction in external potassium concentration. There is no appreciable change in the intracellular sodium concentration, but the relative sodium permeability of the active membrane increases during hyposmotic adaptation. This increase partially compensates for the reduction in sodium gradient across the axon membrane, during dilution of the bathing media, by increasing the overshoot of the action potentials recorded in hyposmotically adapted axons.

Transepithelial and intracellular potentials in isolated Malpighian tubules of tenebrionid beetle

1987 ◽  
Vol 252 (4) ◽  
pp. F645-F653 ◽  
Author(s):  
S. W. Nicolson ◽  
L. C. Isaacson
Keyword(s):  
Membrane Potential ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
Bathing Medium ◽  
Intracellular Potentials ◽  
Tenebrionid Beetle ◽  
Fold Reduction ◽  
K Concentration ◽  
Opposing Effects

Malpighian tubules of Onymacris plana (Coleoptera: Tenebrionidae) have been isolated for measurement of transepithelial and intracellular potentials, before and during stimulation of fluid secretion. In a bathing medium resembling the hemolymph composition of the insect, the transepithelial potential (VT) was approximately 13 mV, lumen positive. VT was subject to drift and frequently showed super-imposed regular oscillations, which were apparently action potentials associated with contractions of muscle fibers running along the tubules. Although tubules of Onymacris are approximately 8 cm long, the basal membrane potential (Vb) did not vary with distance along the tubule, averaging -31 mV. Addition of adenosine 3',5'-cyclic monophosphate (cAMP) or diuretic hormone (DH) homogenate to the bathing medium had no effect on Vb, but opposing effects on VT: cAMP caused it to increase to 60 mV, whereas DH homogenate caused a rapid drop in VT to almost zero. Ion substitutions in the bathing medium showed that under control conditions beetle tubules possessed appreciable basal permeability to both K and Cl ions, with a 10-fold reduction in bath K concentration hyperpolarizing Vb by 54 mV. The basal K and Cl channels were partially blocked by barium and thiocyanate ions, respectively. Stimulation with cAMP increased the apical membrane potential (Va) and significantly reduced the Cl permeability of the basal membrane, whereas its Na permeability remained negligible.

Ion-selective electrode studies on the effects of 5-hydroxytryptamine on the intracellular level of potassium in an insect salivary gland

1978 ◽  
Vol 72 (1) ◽  
pp. 203-216 ◽  
Author(s):  
M. J. Berridge ◽  
W. R. Schlue
Keyword(s):  
Salivary Gland ◽  
Salivary Glands ◽  
Potassium Concentration ◽  
Ionic Composition ◽  
Fluid Secretion ◽  
Ion Selective Electrode ◽  
Intracellular Level ◽  
Rapid Loss ◽  
Selective Electrode ◽  
External Concentration

Potassium-sensitive microelectrodes were used to measure the intracellular level of potassium in Calliphora salivary glands. During stimulation with 1 X 10(−8) M 5-HT, the potassium concentration increased from a resting level of 133.2 to 139.0 mM. When the external concentration of potassium was reduced below 2mM there was a rapid loss of potassium which could be partially reversed by 5-HT. During 5-HT stimulation, the addition of ouabain had no effect on a number of parameters including the rate of fluid secretion, the ionic composition of the saliva and the intracellular level of potassium. The possibility that potassium enters the cells passively is discussed.

The electrical response of isolated salivary glands during stimulation with 5-hydroxytryptamine and cyclic AMP

1971 ◽  
Vol 262 (842) ◽  
pp. 111-120 ◽  
Keyword(s):  
Cyclic Amp ◽  
Salivary Glands ◽  
Electrical Response ◽  
Liquid Paraffin ◽  
Fluid Secretion ◽  
Positive Potential ◽  
Bathing Medium ◽  
Gap Technique ◽  
Rapid Changes ◽  
Continuous Potential

Rate of fluid secretion by the salivary glands of the blowfly Calliphora is regulated by 5-hydroxytryptamine (5-HT) working in conjunction with cyclic AMP. Although cyclic AMP can exactly mimic the acceleration of fluid secretion produced by 5-HT, the underlying electrical events are completely different. Transepithelial potentials were measured by a liquid paraffin-gap technique which permits continuous potential recordings during rapid changes of the bathing medium. The potential of the lumen of unstimulated glands is + 5 mV with respect to the bathing medium but becomes — 10 to 20 mV after applying 5-HT. After stimulation with cyclic AMP, however, the luminal potential becomes more positive (+ 30 to 40 mV). A similar effect is obtained with theophylline or when glands are treated with 5-HT in the presence of an impermeant anion such as isethionate. These observations suggest that in addition to stimulating the synthesis of cyclic AMP, 5-HT may also act directly to increase anion movement. Cyclic AMP appears to stimulate cation transport, which explains the increase in positive potential obtained when this compound (or theophylline) is applied in the absence of 5-HT.

Stimulus-secretion coupling in an insect salivary gland: cell activation by elevated potassium concentrations

1975 ◽  
Vol 62 (3) ◽  
pp. 629-636
Author(s):  
M. J. Berridge ◽  
B. D. Lindley ◽  
W. T. Prince
Keyword(s):  
Salivary Glands ◽  
Cell Activation ◽  
Gland Cell ◽  
Fluid Secretion ◽  
Salivary Gland Cell ◽  
Primary Role ◽  
High Potassium ◽  
External Potassium ◽  
Stimulus Secretion Coupling ◽  
External Calcium

1. Fluid secretion by isolated salivary glands was stimulated by elevating the external potassium concentration. 2. The stimulatory effect of potassium was dependent on external calcium and was potentiated by a subthreshold dose of 5-hydroxytryptamine (5-HT). 3. During the action of 120 mM potassium there was a large calciumdependent decrease in transepithelial resistance similar to that produced with 5-HT at normal potassium concentrations. 4. These results on Calliphora salivary glands are compared with other cases where cells are activated by high potassium. In most cases, the effect of high potassium is dependent upon calcium, suggesting that the latter plays a primary role in cell activation.

Urine Formation by the Malpighian Tubules of Calliphora

1968 ◽  
Vol 48 (1) ◽  
pp. 159-174
Author(s):  
M. J. BERRIDGE
Keyword(s):  
Osmotic Pressure ◽  
Potassium Concentration ◽  
Malpighian Tubules ◽  
Apical Surface ◽  
Bathing Medium ◽  
Sodium Potassium ◽  
Basal Plasma ◽  
External Potassium ◽  
Potassium Secretion ◽  
Urine Formation

1. Rate of urine formation is very sensitive to potassium concentration. 2. Potassium is concentrated in the urine by a mechanism which is independent of other monovalent cations. Rubidium, caesium and sodium are also capable of maintaining a flow of urine. At low external potassium concentrations, sodium stimulates potassium secretion. 3. Rate of urine secretion is stimulated by low osmotic pressures; the osmotic pressure of urine was slightly hypertonic throughout the range of external osmotic pressure employed. Addition of sucrose depresses rate of urine secretion; the potassium concentration of the urine increased by 1 mM/l. for each 2 mM/l. of sucrose added to the bathing medium. 4. Urine formation is insensitive to sulphanilamide, acetazolamide, ouabain and a wide variation of pH. 5. These observations are discussed in relation to the hypothesis that potassium secretion takes place across both surfaces of the cell. The pump on the basal surface may be a coupled sodium-potassium pump, whereas that on the apical surface may be electrogenic. 6. Microvilli at the apical surface or channels formed by a complex infolding of the basal plasma membrane may represent structural devices by which standing osmotic gradients can be established during solute-linked water transport across the cells of Malpighian tubules.

The Role of Calcium in the Action of 5-Hydroxytryptamine and Cyclic Amp on Salivary Glands

1973 ◽  
Vol 58 (2) ◽  
pp. 367-384
Author(s):  
WILLIAM T. PRINCE ◽  
MICHAEL J. BERRIDGE
Keyword(s):  
Cyclic Amp ◽  
Salivary Glands ◽  
Normal Saline ◽  
Mode Of Action ◽  
Apical Membrane ◽  
Potential Response ◽  
Chloride Medium ◽  
Bathing Medium ◽  
Calcium Dependent

1. The role of calcium in the potential and secretory responses of isolated salivary glands of Calliphora to 5-HT and cyclic AMP has been studied. 2. Secretion induced by 5-HT was reversibly inhibited by removal of calcium from the bathing medium. 3. The chloride-dependent depolarization of the apical membrane produced by 5-HT was calcium dependent whereas the potential response to cyclic AMP was little effected. 4. Strontium and barium effectively substituted for calcium. 5. Manganese replaced calcium at the onset of secretory and potential responses but these responses were maintained when manganese was removed. 6. Lanthanum did not substitute for calcium in secretory responses but did inhibit the secretory and potential responses to calcium in calcium-depleted glands. 7. The rate of secretion in a low-chloride medium produced by cyclic AMP was significantly lower than that induced by 5-HT, but there was little difference in normal saline. 8. A model for the mode of action of 5-HT is proposed in which calcium acts as an intracellular intermediary controlling chloride movements whilst cyclic AMP controls a potassium pump.

scholarly journals Mechanisms of K+ uptake across the basal membrane of malpighian tubules of Formica polyctena: the effect of ions and inhibitors.

1994 ◽  
Vol 195 (1) ◽  
pp. 123-145 ◽  
Author(s):  
A Leyssens ◽  
S Dijkstra ◽  
E Van Kerkhove ◽  
P Steels
Keyword(s):  
Membrane Potential ◽  
Electrical Potential ◽  
Basal Membrane ◽  
Fluid Secretion ◽  
Malpighian Tubules ◽  
K Uptake ◽  
Bathing Medium ◽  
K Channels ◽  
High K ◽  
K Concentration

In the presence of 6 mmol l-1 Ba2+, known to block the K+ channels in the basal membrane, a rise in bath [K+] ([K+]bl) induced an increase in intracellular K+ concentration ([K+]i) similar in amount and in time course to that obtained in the absence of Ba2+. The presence of active and passive (other than through K+ channels) K+ uptake mechanisms across the basal membrane was investigated in different bath K+ concentrations. Dihydro-ouabain (10(-3) mol l-1), a blocker of the Na+/K(+)-ATPase, tested in low bath [K+], and Sch28080 (10(-4) mol l-1), a K+/H(+)-ATPase inhibitor, were without effect on fluid secretion. Dihydro-ouabain was also without effect on electrical potential differences either in the absence or in the presence of Ba2+. Vanadate (10(-3) mol l-1), in contrast, strongly reduced fluid secretion not only in control solution but also in high-K+, Na(+)-free medium and reduced the transepithelial and the apical membrane potential differences but not the basal membrane potential difference of [K+]i. Omitting Na+ from the bathing medium, replacing Cl- by Br- or applying bumetanide (10(-5) mol l-1) inhibited fluid secretion only in a low-K+ (10 mmol l-1) medium. In 51 mmol l-1 [K+]bl, omitting Na+ was without effect and 10(-4) mol l-1 bumetanide was needed to inhibit secretion. Replacing Cl- by Br- stimulated fluid secretion at this K+ concentration. Bumetanide (10(-4) mol l-1) had no effect in 113 mmol l-1 [K+]bl. Bumetanide (10(-4) mol l-1) in 51 mmol l-1 [K+]bl did not affect membrane potentials, did not lower [K+]i and did not affect the rise in [K+]i observed on an increase in [K+]bl. The results were summarized in a model proposing that K+ channels play a dominant role in high-K+ (113 mmol l-1) bathing medium. A K+/Cl- cotransporter may become more important in 51 mmol l-1 [K+]bl and a K+/Na+/2Cl- cotransporter may gain in importance in 10 mmol l-1 [K+]bl. Active mechanisms for K+ uptake across the basal membrane seem to play no detectable role in sustaining fluid secretion. The response to vanadate might be due to an effect on the apical electrogenic H+ pump.

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