Calcium mobilization and phosphatidylinositol turnover in vas deferens smooth muscle of diabetic rats.
The study concerned Ca2+ channels that are receptor-operated by norepinephrine (NE) and mediate hyper-reactivity of vas deferens smooth muscle from rats with streptozotocin (STZ)-induced diabetes, and the mediatory responses of these channels, such as tension development, Ca2+ uptake and phosphatidylinositol (PI) turnover. The contractile responses induced by adrenoceptor agonists were significantly greater in diabetic rat vas deferens than in the controls. A greater Ca2+ uptake was induced by 10(-5) M NE in strips from diabetic rats than in the controls. The uptake of Ca2+ was completely inhibited by 10(-6) M prazosin but not by 10(-5) M verapamil. Enhancement of Ca2+ release by 10(-5) M NE was faster and greater in diabetic muscles than in the controls. The accumulation of [3H]inositol phosphates was increased 4-fold in the controls and 7-fold in diabetic muscles by 10(-5) M NE. This increase was completely inhibited by 10(-6) M prazosin but not by 10(-6) M yohimbine. The data suggest that vas deferens smooth muscle hyper-reactivity in diabetic rats is due to increased PI turnover mediated by alpha 1-adrenoceptors, to the release of intracellular bound Ca2+ and to an increase of Ca2+ uptake through receptor-operated Ca2+ channels.
Sakai
Y
Y
2nd Department of Physiology, Showa University, School of Medicine, Tokyo, Japan.
Aihara
K
K
Honda
H
H
Inazu
M
M
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism*; D066298:In Vitro Techniques; D007294:Inositol / Q000378:metabolism; D008055:Lipids / Q000096:biosynthesis; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D010716:Phosphatidylinositols / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013566:Sympathomimetics / Q000494:pharmacology; D014649:Vas Deferens / Q000378:metabolism
D002132:Calcium Radioisotopes; D008055:Lipids; D010716:Phosphatidylinositols; D013566:Sympathomimetics; D007294:Inositol; D002118:Calcium; D009638:Norepinephrine