Different alpha(1)-adrenoceptor-induced inositol phosphate formation in the two portions of rat vas deferens

The two portions of rat vas deferens differed in the postjunctional sensiti vity to noradrenaline. al-Adrenoceptor-linked phosphoinositide breakdown wa s analysed in this tissue. The noradrenaline-induced [H-3]inositol phosphat e accumulation was similar in both ends although the pEC(50)was higher in t he epididymal (5.97 +/- 0.07) than in the prostatic (5.47 +/- 0.15, P < 0.0 1) portion. [H-3]Prazosin showed similar density of binding sites in both p ortions. Tissue pretreated with pertussis toxin did not change [H-3]inosito l phosphate accumulation. Finally, Western blot analysis indicated a smalle r concentration of G(q/11) protein in the prostatic half (-29 +/- 5%, P < 0 .01). These results suggest that the different sensitivity to noradrenaline could be due to the higher availability of this sort of G protein in the e pididymal portion.