title: Time-dependent alteration in cromakalim-induced relaxation of corpus cavernosum from streptozocin-induced diabetic rats.
abstract: The purpose of the present study was to investigate the relaxant responses to the ATP-sensitive potassium (K(ATP)) channel opener cromakalim in corpus cavernosum strips from 1-, 2-, 4-, 6-, and 8-week streptozocin-induced diabetic rats. Cromakalim (1 nM-0.1 mM) produced concentration-dependent relaxation in phenylephrine (7.5 microM)-precontracted isolated rat corporal strips. Compared with age-matched control animals, a significant enhancement in cromakalim-induced relaxation of corpus cavernosum was observed in 2-week diabetic animals, whereas the relaxant responses to cromakalim were decreased in 6-and 8-week diabetic animals. However, the cromakalim-induced relaxation was not altered in either 1-week or 4-week rat corporal strips in comparison with corresponding age-matched non-diabetic groups. Preincubation with the K(ATP) channel blocker glibenclamide (10 microM) significantly inhibited the cromakalim-induced relaxation in both non-diabetic and diabetic rat corpus cavernosum, but neither the voltage-dependent K(+) channel (K(V)) antagonist 4-aminopyridine (1 mM) nor the calcium-activated K(+) channel (K(Ca)) antagonist charybdotoxin (0.1 microM) had significant effect on cromakalim-induced relaxation in both control and diabetic rat corporal strips. Relaxation responses to the nitric oxide donor sodium nitroprusside (1 nM-0.1 mM) in diabetic rat corpus cavernosum were similar to that of age-matched controls. These data demonstrated that the relaxant responses to cromakalim were altered in diabetic cavernosal strips in a time dependent manner, suggesting that the period of diabetes mellitus may play a key role in the K(ATP) channels function in rat corpus cavernosum.
authors.affiliation: Department of Pharmacology, School of Medicine, Medical Sciences / University of Tehran, PO Box: 13145-784, Tehran, Iran.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Ghasemi
authors.forename: Hamed
authors.initials: H
authors.lastname: Sadeghipour
authors.forename: Shahrzad
authors.initials: S
authors.lastname: Asadi
authors.forename: Ahmad Reza
authors.initials: AR
authors.lastname: Dehpour
mesh_terms: D000818:Animals; D019806:Cromakalim / Q000494:pharmacology*; D003921:Diabetes Mellitus, Experimental / Q000503:physiopathology*; D004305:Dose-Response Relationship, Drug; D005905:Glyburide / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009126:Muscle Relaxation / Q000187:drug effects*; D010413:Penis / Q000187:drug effects* / Q000502:physiology; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D051381:Rats; D017207:Rats, Sprague-Dawley; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013311:Streptozocin; D013997:Time Factors