We investigated, in isolated bile duct units (IBDU) and cholangiocytes isolated from normal rat liver, the occurrence of acetylcholine (ACh) receptors, and the role and mechanisms of ACh in the regulation of the Cl Ϫ /HCO 3 Ϫ exchanger activity. The Cl Ϫ /HCO 3 Ϫ exchanger activity was evaluated measuring changes in intracellular pH induced by acute Cl Ϫ removal/readmission. M3 subtype ACh receptors were detected in IBDU and isolated cholangiocytes by immunofluorescence, immunoelectron microscopy, and reverse transcriptase PCR. M1 subtype ACh receptor mRNA was not detected by reverse transcriptase PCR and M2 subtype was negative by immunofluorescence. ACh (10 M) showed no effect on the basal activity of the Cl Ϫ /HCO 3 Ϫ exchanger. When IBDU were exposed to ACh plus secretin, ACh significantly ( P Ͻ 0.03) increased the maximal rate of alkalinization after Cl Ϫ removal and the maximal rate of recovery after Cl

The plasma metabolic clearance of biologically active luteinizing hormone (bioactive LH) was studied using the rat interstitial cell testosterone (RICT)

ACTH and beta-endorphin have been evaluated by means of a specific and sensitive radioimmunoassay in athletes reaching a status of physical stress. A concomitant marked increase of these 2 peptides has been recorded. The implications of this finding lead to the conclusion that stress stimulates the synthesis of the common precursor (31 K) in the pituitary.