Relaxation of the bovine retractor penis muscle by a small K+ excess and the role of K+ in its neurogenic relaxation.
The mechanism of the relaxation of the bovine retractor penis muscle induced by 6.7 mM K+ as well as the role of K+ in the neurogenic relaxation of this muscle induced by nicotine, acetylcholine or electrical field stimulation, was studied. The relaxation induced by 6.7 mM K+ was, contrary to that induced by nicotine or electrical field stimulation, abolished by 10(-7) M ouabain. 15 min exposure to 10(-5) M NG-nitro-L-arginine, 3.2 x 10(-6) M tetrodotoxin, 5.0 x 10(-4) M hexamethonium, 5.3 x 10(-4) M methylene blue or hypoxia, all known to inhibit the neurogenic relaxation, did not affect the relaxation induced by 6.7 mM K+, which was also unaffected by 10(-5) M apamin, 3 x 10(-3) M 4-aminopyridine, 2.6 x 10(-2) M tetraethylammonium and 7.3 x 10(-4) M Ba2+. Exposure to K(+)-free solution reversibly abolished the neurogenic relaxations. The relaxations caused by 5.0 x 10(-7) M cromakalim and 2.0 x 10(-6) M pinacidil were totally blocked by 10(-5) M glibenclamide. Glibenclamide and apamin did not affect the tone of the muscle or its neurogenic relaxations. 4-Aminopyridine 4.0 x 10(-5) to 3.0 x 10(-3) M and tetraethylammonium 10(-4) to 2.6 x 10(-2) M raised the tone and enhanced the relaxations elicited by electrical field stimulation. The results indicate that the relaxation induced by 6.7 mM K+ is partly mediated by activation of Na(+)-K(+) ATPase and that its mechanism is thoroughly different from that of the neurogenic relaxations.(ABSTRACT TRUNCATED AT 250 WORDS)
Alaranta
S
S
Department of Pharmacy, University of Helsinki, Finland.
Klinge
E
E
Kostiainen
E
E
Parkkisenniemi
U M
UM
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D004558:Electric Stimulation; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D009130:Muscle, Smooth; D009538:Nicotine / Q000494:pharmacology; D010042:Ouabain / Q000494:pharmacology; D010413:Penis / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology*; D014665:Vasodilator Agents / Q000494:pharmacology
D014665:Vasodilator Agents; D010042:Ouabain; D009538:Nicotine; D000109:Acetylcholine; D011188:Potassium