Phorbol ester stimulation of active anion secretion in intestine

Abstract

Phorbol 12,13-dibutyrate (PDB) stimulates electrogenic anion secretion in rabbit and chicken distal ileum. The 50% effective dose in each case was 15 nM, and the maximal short-circuit current (Isc) responses seen at 10(-6) M were 20 and 140 microA/cm2, respectively. Isc was also stimulated by the diacylglycerol 1-oleoyl-2-acetyl glycerol (10(-5) M) but not by the inactive phorbol ester analogue 4 alpha-phorbol 12,13-didecanoate. Removal of Ca from the serosal bathing medium and pretreatment of tissues with atropine (10(-6) M) or tetrodotoxin (2 X 10(-7) M) did not affect PDB-stimulated responses. PDB also did not alter basal intracellular free Ca levels in isolated chicken enterocytes loaded with quin 2 or basal adenosine 3',5'-cyclic monophosphate levels in intact tissues from rabbit and chicken. In the presence of PDB, Ca- and phospholipid-dependent phosphorylation of several proteins in particulate and soluble fractions from isolated chicken enterocytes were seen. Pretreatment of chicken and rabbit tissues with indomethacin or mepacrine inhibited the Isc responses to PDB and carbamylcholine, suggesting a role for prostaglandins. These results suggest that electrogenic anion secretion stimulated by phorbol esters and diacylglycerol may be mediated by activation of protein kinase C.

Carbachol- and elevated Ca(2+)-induced translocation of functionally active protein kinase C to the brush border of rabbit ileal Na+ absorbing cells.

“…The time course of the carbachol-induced translocation ofprotein kinase C, which is reported here, is different from that reported to occur in chicken small intestine in response to phorbol dibutyrate (26). In the latter, the phorbol ester treatment caused a transient (90 s) increase in microvillus protein kinase C activity which returned to control levels by 15 min (26).…”

“…Initially, protein kinase C was suggested as stimulating all Na+/H' exchangers. Now, with few exceptions (27), protein kinase C has been found to inhibit both intestinal and renal apical membrane Na+/H' exchangers but to stimulate their basolateral Na+/H' exchangers (3,26,(28)(29)(30). Whether it is the location in the plasma membrane, the molecular nature of the Na+/H' exchangers, or the subtype of protein kinase C involved which accounts for this differential regulation remains unknown.…”

Immune system control of rat and rabbit colonic electrolyte transport. Role of prostaglandins and enteric nervous system.

“…These studies, however, do not rule out a role for lipoxygenase products in immune system-mediated alterations in electrolyte transport. Lipoxygenase products do alter intestinal electrolyte transport in the Ussing Chamber (6,42 The electrolyte transport responses reported here have been noted to some degree with other immune cell stimulants such as leukotrienes (6), phorbol esters (49,50) and interleukins (51). The responses to these agonists are all partially inhibited by cyclooxygenase blockers.…”

Effects of protein kinase C activation on sodium, potassium, chloride, and total CO2 transport in the rabbit cortical collecting tubule.

“…Finally, we examined the effects ofperitubular PMA on net chloride transport in the rabbit CCT since phorbol esters stimulate Cl secretion in rabbit (25) and rat (26) small intestine and rat colon (27). There was no significant effect of peritubular addition of 2.5 X 10-8 M PMA on net Cl absorption in six rabbit CCTs.…”

“…We next examined the effect of peritubular PMA on the net transport of total CO2 in the rabbit CCT. These studies are important because activation of protein kinase C stimulates bicarbonate secretion in Vero cells (from African green monkey kidney [24]), and chicken and rabbit small intestine (25).…”