Interactions of TPA and insulin on Na+ transport across frog skin

Civan, Mortimer M.; Peterson-Yantorno, K.; George, Kenneth; O’Brien, Thomas G.

doi:10.1152/ajpcell.1989.256.3.c569

Cited by 9 publications

(12 citation statements)

References 50 publications

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“…We have previously reported that PKC activation inhibits the subsequent natriferic response to cAMP (Civan et al, , 1989Mauro et al, 1987). In the present study, we have found that reducing Ca 2+ cytosolic entry from the extracellular fluid or from the endoplasmic reticulum reduces the PKC-triggered natriferic response.…”

Section: Introductionsupporting

confidence: 60%

“…PKC stimulates Na + transport across frog skin epithelium by as much as 40-60% (Civan et al, 1989). The natriferic action appears to reflect an increase in Pa~P a (Civan et al, , 1989.…”

Section: Introductionmentioning

confidence: 92%

“…Each train comprised 12 pairs of alternately hyperpolarizing and depolarizing pulses, the magnitude increasing by 20 mV in successive steps (DeLong & Civan, 1984;Leibowich, DeLong & Civan, 1988). Data were acquired with pulse durations of 16 or 32 msec and interpulse intervals of 240-640 msec, but the choice of pulse duration is not critical (Civan et al, 1989). The final eight data points (for tome to m~ and It) were sampled at each voltage step over a period of 0.96 msec.…”

Section: Intracellular Measurementsmentioning

confidence: 99%

“…Activators of protein kinase C (PKC) also have marked effects on Na + transport across frog skin (Civan et al, , 1989Civan, Petersen-Yantorno & O'Brien, 1987, 1988Andersen, Bjerregaard & Nielsen, 1987;Mauro, O'Brien & Civan, 1987). PKC stimulates Na + transport across frog skin epithelium by as much as 40-60% (Civan et al, 1989).…”

Section: Introductionmentioning

confidence: 99%

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Ca2+-independent form of protein kinase C may regulate Na+ transport across frog skin

et al. 1991

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Activators of protein kinase C (PKC) stimulate Na+ transport (JNa) across frog skin. We have examined the effect of Ca2+ on PKC stimulation of JNa. Both the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) and the diacyl-glycerol sn-1,2-dioctanoylglycerol (DiC8) were used as PKC activators. Blocking Ca2+ entry into the cytosol (either from external or internal stores) reduced the subsequent natriferic effect of the PKC activators. This negative interaction did not simply reflect saturation of activation of the apical Na+ channels, since the stimulations produced by blocking Ca2+ entry and adding cyclic AMP were simply additive. The Ca2+ dependence of the natriferic effect could have reflected either a direct action of cytosolic Ca2+ on PKC or an indirect action on the final receptor site (the Na+ channel). To distinguish between these possibilities, the TPA- and phospholipid-dependent kinase activity of broken-cell preparations was assayed. The kinase activity was not stimulated by physiological levels of Ca2+, and in fact was inhibited at millimolar concentrations of Ca2+. We conclude that the effects of Ca2+ on the natriferic response to PKC activators are indirect. Reducing cytosolic uptake of Ca2+ may have stimulated Na+ transport by a chemical modification of the apical channels observed in other tight epithelia. The usual stimulation of Na+ transport produced by PKC activators in frog skin may reflect the operation of a nonconventional form of PKC. This enzyme is Ca2+ independent and seems related to the nPKC or PKC epsilon observed in other systems.

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Section: Introductionsupporting

confidence: 60%

“…PKC stimulates Na + transport across frog skin epithelium by as much as 40-60% (Civan et al, 1989). The natriferic action appears to reflect an increase in Pa~P a (Civan et al, , 1989.…”

Section: Introductionmentioning

confidence: 92%

Section: Intracellular Measurementsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ca2+-independent form of protein kinase C may regulate Na+ transport across frog skin

et al. 1991

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“…Although it has been disputed, PKC has been proposed as a mediator for some effects of insulin (e.g. hexone transport [ 12], lipogenesis [13], sodium trans port [14] and glucose carrier translocation [15]). On the other hand, tumor-promoting esters (e.g.…”

mentioning

confidence: 99%

Effect of Insulin on Hydrogen Peroxide Production by Human Polymorphonuclear Leukocytes

Spagnoli

Spadoni²,

Sesti

et al. 1995

Horm Res

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This study evaluated the effect of insulin on the respiratory burst of human polymorphonuclear leukocytes (PMNLs) and the signalling pathways involved in this process, especially the involvement of protein kinase C (PKC). Isolated human PMNLs from healthy volunteers were incubated with different concentrations of insulin (10^-10-10^-7 mol/l) and for different durations of incubation (5-90 min). The intracellular production of hydrogen peroxide (H₂O₂) was detected employing a previously validated flow cytometric assay using 2’,7’-dichlorofluorescein-diacetate (DCFH-DA) as a marker for H₂O₂production. Specificity of insulin action was verified using an insulin antagonist (the monoclonal antibody MA-10). To identify the signalling pathway involved, we used: (a) monoclonal antibody MA-5, directed against the α-subunit of the insulin receptor, that partially mimics insulin without activating tyrosine kinase; (b) H7, an inhibitor of PKC involved in O₂^- production in PMNLs, and (c) phorbol myristate acetate (PMA) that binds and stimulates PKC. Insulin caused a dose- and time-dependent stimulation of H₂O₂ release by human PMNLs. The effect of insulin was blocked by MA-10. The actions of insulin and PMA on H₂O₂ release were additive, whereas the actions of MA-5 and PMA were not. H7 partially inhibited the H₂O₂ production stimulated by insulin and completely inhibited MA-5 action. We conclude that insulin stimulates, in a dose- and time-related manner, the respiratory burst of human PMNLs. PKC activation can only partially account for the intracellular mechanisms involved in this process.

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Modulation of the Na–;H antiport by insulin: Interplay between protein kinase C, tyrosine kinase, and protein phosphatases

Incerpi¹,

Baldini²,

Bellucci³

et al. 1994

Journal Cellular Physiology

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The insulin modulation of Na-H antiport in rat hepatocytes was studied using the fluorescent, pH-sensitive intracellular probe, 2',7' bis (carboxyethyl)-5(6)-carboxyfluorescein (BCECF). Our data show that insulin stimulates the Na-H antiport. The dose-response of insulin effect shows a behavior typical of other insulin responses: a maximum in the physiological range (1 nM) and smaller effects at higher and lower hormone concentrations. The time-course of activation is very fast at high hormone concentrations and slow, but reaching a higher value, for the physiological concentrations (0.26 +/- 0.05 and 0.18 +/- 0.022 pH units for 1 nM and 1 microM insulin respectively). The use of phorbol, 12-myristate, 13-acetate (PMA), a potent activator of protein kinase C and its inhibitor staurosporine, and the inhibitor of tyrosine kinase erbstatin analog, suggests that both protein kinase C and tyrosine kinase could be involved in the mechanism leading to Na-H antiport activation by insulin. We suggest that the activation of the antiport involves the two pathways depending on the hormone concentration. In particular, protein kinase C would mediate the effects of high hormone concentrations, acting as a growth factor, since staurosporine fully inhibited insulin 1 microM, but only partially 1 nM effects, and tyrosine kinase would mediate the effect of insulin 1 nM and only partially 1 microM. Okadaic acid 1 microM, a potent inhibitor of protein phosphatases, mimicked the hormone effects on the antiport and abolished the different time-course due to hormone concentration, suggesting a role of kinases and phosphatases in the signal transduction. The effect of all activators was abolished by amiloride analog, 5-(N-ethyl-N-isopropyl) amiloride (EIPA), confirming the specificity of these effects.

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Interactions of TPA and insulin on Na+ transport across frog skin

Cited by 9 publications

References 50 publications

Ca2+-independent form of protein kinase C may regulate Na+ transport across frog skin

Ca2+-independent form of protein kinase C may regulate Na+ transport across frog skin

Effect of Insulin on Hydrogen Peroxide Production by Human Polymorphonuclear Leukocytes

Modulation of the Na–;H antiport by insulin: Interplay between protein kinase C, tyrosine kinase, and protein phosphatases

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