Morphological and functional characteristics of isolated acini used for in vitro studies of prostatic secretion

Acini of the rat ventral prostate were isolated by interstitial injection of a collagenase-containing medium, subsequent incubation in the same medium and repeated aspiration through pipette tips with decreasing gauge of the tip opening. Functional integrity of the isolated acini was assessed by morphological studies, including transmission and scanning electron microscopy, freeze-fracturing, and immunocytochemistry. Incubation studies with different incubation media were performed monitoring O2-consumption as a parameter of functional activity, in addition to the incorporation rate of radioactively labeled amino acids into newly synthesized proteins. Optimal incubation conditions (shaking water bath, 20 strokes/min, 37 degrees C, gassing with carbogen at 15 min intervals) were found with M 199 medium supplemented with dihydrotestosterone. Stimulation of prostatic secretion was maximal with 10(-7) M of pilocarpin, which was more effective than carbamylcholine. Incorporation of precursors into prostatic proteins proceeded for about 2 h at a linear rate. Thereafter a rapid loss of functional and morphological integrity of the isolated acini was observed including disintegration, vacuolation and lysis of individual cells. The system of isolated prostatic epithelium developed is a useful tool in the study of prostatic secretion in vitro in short term experiments.