Effect of short-term bile duct ligation on peripheral blood steroids, urinary PGE2 and the rate of sodium excretion in male rabbits

Progesterone stimulates the proliferation of female and male cholangiocytes via autocrine/paracrine mechanisms

During cholestatic liver diseases, cholangiocytes express neuroendocrine phenotypes and respond to a number of hormones and neuropeptides by paracrine and autocrine mechanisms. We examined whether the neuroendocrine hormone progesterone is produced by and targeted to cholangiocytes, thereby regulating biliary proliferation during cholestasis. Nuclear (PR-A and PR-B) and membrane (PRGMC1, PRGMC2, and mPRalpha) progesterone receptor expression was evaluated in liver sections and cholangiocytes from normal and bile duct ligation (BDL) rats, and NRC cells (normal rat cholangiocyte line). In vivo, normal rats were chronically treated with progesterone for 1 wk, or immediately after BDL, rats were treated with a neutralizing progesterone antibody for 1 wk. Cholangiocyte growth was measured by evaluating the number of bile ducts in liver sections. The expression of the progesterone synthesis pathway was evaluated in liver sections, cholangiocytes and NRC. Progesterone secretion was evaluated in supernatants from normal and BDL cholangiocytes and NRC. In vitro, NRC were stimulated with progesterone and cholangiocyte supernatants in the presence or absence of antiprogesterone antibody. Aminoglutethimide was used to block progesterone synthesis. Cholangiocytes and NRC express the PR-B nuclear receptor and PRGMC1, PRGMC2, and mPRalpha. In vivo, progesterone increased the number of bile ducts of normal rats, whereas antiprogesterone antibody inhibited cholangiocyte growth stimulated by BDL. Normal and BDL cholangiocytes expressed the biosynthetic pathway for and secrete progesterone. In vitro, 1) progesterone increased NRC proliferation; 2) cholangiocyte supernatants increased NRC proliferation, which was partially inhibited by preincubation with antiprogesterone; and 3) inhibition of progesterone steroidogenesis prevented NRC proliferation. In conclusion, progesterone may be an important autocrine/paracrine regulator of cholangiocyte proliferation.

Rapid increase in plasma levels of atrial natriuretic peptide after common bile duct ligation in the rabbit

Previous studies have shown that common bile duct ligation in the rabbit is followed by a reduction of the extracellular water compartment. To further elucidate the mechanisms leading to volume depletion in this model, water and sodium balances and changes in plasma concentrations of atrial natriuretic peptide (ANP), vasopressin (ADH), plasma renin activity (PRA) and aldosterone (Ald) were investigated during the first 4 days after common bile duct ligation (group OJ,) or sham operation (group SO). Water and chow intakes were lower in group OJ (148 +/- 30 versus 226 +/- 40 mL/4 days; p = 0.004 and 12 +/- 9 versus 171 +/- 40 g/4 days; p = 0.0001). There were no differences in urine output. Sodium urinary losses were marginally higher in group OJ (12.4 +/- 7 versus 6.7 +/- 5 mEq/4 days; p = 0.06). Water balance was lower in group OJ (-50 +/- 56 versus 101 +/- 71 mL/4 days; p = 0.0001). At 24 hours, plasma ANP (41 +/- 7 versus 10.7 +/- 1 fmol/mL, p = 0.0001), ADH (21.8 +/- 7 versus 12.3 +/- 6 pg/mL, p = 0.008) and Ald (14.5 +/- 5 versus 3.7 +/- 3 ng/dL, p = 0.001) were higher in group OJ. These alterations persisted 72 hours after bile duct ligation, when a concomitant increase in PRA (10.7 +/- 5 versus 3 +/- 1.6 ng/dL, p = 0.006) was also observed. A group of pair-fed pair-watered sham-operated controls (group SO2, n = 13) showed a metabolic profile similar to group OJ but a low ANP concentration. Multiple venous sampling in five rabbits 24 hours after bile duct ligation showed the highest plasma levels of ANP in the aorta and infrarenal vena cava. These results suggest that common bile duct ligation in the rabbit is followed by marked hypodipsia and hypophagia, possibly mediated by ANP, leading to isotonic volume depletion and secondary activation of the water and sodium retaining hormones.

Effect of sodium taurocholate and sodium cholate on short-circuit current on amphibian membranes

The effects of the bile salts, sodium taurocholate (NaTc) and sodium cholate (NaCh), and toad bile gallbladder (bile) on short-circuit current (SCC) across isolated skin, and sodium taurocholate (NaTc) on isolated bladder of Bufo arenarum toads were tested. Sodium taurocholate (NaTc), sodium cholate (NaCh) and toad bile gallbladder (bile) promoted an increase in SCC, when added to the external side. The stimulatory effect was reversible after rinsing the preparation for 60 min. Implications on in vivo renal function of these results are discussed.