Sustained recovery of Na(+)-K(+)-ATPase activity in sciatic nerve of diabetic mice by administration of H7 or calphostin C, inhibitors of PKC.
We have previously shown that intraperitoneal injection of H-7, an inhibitor of PKC, restores completely the activity of Na(+)-K(+)-ATPase in sciatic nerve of diabetic mice; however, the effect was transient, with a half-life of approximately 1 h under the conditions used. This work assessed whether calphostin C, a new more potent and specific inhibitor of PKC, is also able to restore the activity of Na(+)-K(+)-ATPase in sciatic nerve of ALX-induced diabetic mice and also assessed if continuous administration of H-7 or calphostin C can afford sustained recovery of the ATPase. Small amounts of calphostin C (i.e., 2 micrograms/kg) restore entirely the activity of the enzyme. Larger doses (e.g., 30 micrograms/kg) can be administered with equal results. The ED50 was approximately 0.5 micrograms/kg. This indicates that calphostin C is approximately 20,000 times more potent than H-7 in restoring the ATPase activity in diabetic mice. A single intraperitoneal injection of 1 or 10 micrograms/kg of calphostin C maintains the enzyme for 4 and 8 h, respectively. Administration of H-7 by continuous delivery from micro-osmotic pumps implanted in the back of the mice maintains the Na(+)-K(+)-ATPase for 24 h, although the activity decreases thereafter. This is the result of instability of H-7 in solution. Continous administration of calphostin C maintains the activity of the ATPase at nearly normal values for at least 2 wk. The results support the hypothesis that, in sciatic nerve tissue of diabetic animals, the activity of PKC is increased, leading to higher phosphorylation of Na(+)-K(+)-ATPase, which results in the decreased activity observed.(ABSTRACT TRUNCATED AT 250 WORDS)
Hermenegildo
C
C
Instituto de Investigaciones Citológicas de la Fundación Valenciana de Investigaciones Biomédicas, Spain.
Felipo
V
V
Miñana
M D
MD
Romero
F J
FJ
Grisolía
S
S
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology*; D004305:Dose-Response Relationship, Drug; D007546:Isoquinolines / Q000494:pharmacology*; D007700:Kinetics; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009281:Naphthalenes; D010879:Piperazines / Q000494:pharmacology*; D011083:Polycyclic Compounds / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors*; D012016:Reference Values; D012584:Sciatic Nerve / Q000187:drug effects / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013997:Time Factors
D007546:Isoquinolines; D009281:Naphthalenes; D010879:Piperazines; D011083:Polycyclic Compounds; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase; C058819:calphostin C