L-arginine-induced relaxation of the rat isolated penile bulb.
The effects of L-arginine, the precursor in the synthesis of nitric oxide (NO), were investigated in the penile bulb isolated from saline (control) or lipopolysaccharide (20 mg/kg, i.p.)-treated rats. Four consecutive concentration-response curves for L-arginine were made at hourly intervals with the penile bulb. L-arginine (10(7)-10(-3) M) elicited a concentration- and time-dependent relaxation response in the control group. The NO synthase (NOS) inhibitors, N(G)-methyl-L-arginine (L-NMMA) and aminoguanidine, guanylate cyclase inhibitor, 1-H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ) and protein synthesis inhibitor, cycloheximide, inhibited L-arginine-induced relaxation. In the lipopolysaccharide-group, L-arginine produced a pronounced non-time-dependent relaxation at the first concentration-response curve, which was not different from the fourth response of the control group. This response was also inhibited by aminoguanidine. These results show that L-arginine induced NO-mediated relaxation and suggest the presence of a biochemical pathway converting L-arginine to NO, which is probably an inducible type in the penile bulb.
Burcin Ismailoglu
U
U
Department of Pharmacology, Faculty of Pharmacy, University of Hacettepe, 06100, Ankara, Turkey.
Sahin-Erdemli
Inci
I
Ilhan
Mustafa
M
D000704:Analysis of Variance; D000818:Animals; D001120:Arginine / Q000494:pharmacology*; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D010413:Penis / Q000187:drug effects* / Q000502:physiology; D051381:Rats
D001120:Arginine