Role of protein kinase C in insulin activation of the Na-K pump in cultured skeletal muscle.
Administration of insulin to preparations of skeletal muscle causes an increase in Na(+)-K+ pump activity within 15-30 min. Although several mechanisms have been proposed, such as promotion of Na+ influx and translocation of pumps from intracellular to membrane sites, the early events involved in this effect remain unknown. We have investigated the possibility that activation of protein kinase C (PKC) may be an initial event in Na(+)-K+ pump activation in primary cultures of rat skeletal muscle. Insulin (80-100 mU/ml) and tumor-promoting phorbol esters (10-100 nM) increased Na(+)-K+ pump activity as determined by measurements of ouabain-suppressible 86Rb uptake, electrogenic pump component of membrane potential, and specific [3H]ouabain binding. These effects were not reduced by treatment of myotubes with amiloride, which blocks Na(+)-H+ exchange, or with tetrodotoxin, which blocks voltage-dependent Na+ channels. Effects of insulin and phorbol esters were not additive, suggestive of a common mechanism. Effects of both phorbol esters and insulin were significantly reduced by staurosporine (50-100 nM) and by downregulation of PKC (by pretreatment of myotubes with phorbol ester for 24 h). The findings suggest that insulin may stimulate Na(+)-K+ pump activity in skeletal muscle by activation of PKC.
Sampson
S R
SR
Health Sciences Research Center, Bar-Ilan University, Ramat Gan, Israel.
Brodie
C
C
Alboim
S V
SV
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D007328:Insulin / Q000494:pharmacology*; D009132:Muscles / Q000166:cytology / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects* / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
D007328:Insulin; D013779:Tetrodotoxin; D010042:Ouabain; D000584:Amiloride; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase