title: The effect of cholera toxin on choroid plexus carbonic anhydrase activity in vitro.
abstract: The effects of the adenylate cyclase agonists cholera toxin and prostaglandin E2 on carbonic anhydrase activity in vitro was measured in choroid plexuses isolated from Sprague-Dawley rats. Choroid plexuses were incubated in buffer at 38 degrees C (pH 7.4) with either cholera toxin or prostaglandin E2 (PGE2) at a concentration and for a time period that had been shown in earlier studies to result in maximal stimulation of cyclic AMP production. Cholera toxin (10 micrograms/ml) caused a twofold increase (p < .001) in choroid plexus carbonic anhydrase activity when cholera toxin treated plexuses [20.92 +/- .46 mol CO2/(min)(mg protein X 10(-8)] were compared with plexuses exposed to heat inactivated cholera toxin (10.92 +/- .43). When choroid plexuses were homogenized and separated into a 10,000 g pellet and a supernatant fraction, the supernatant carbonic anhydrase was unresponsive to cholera toxin stimulation. In the pellet fraction, which contained all the cellular adenylate cyclase, challenge with cholera toxin produced a significant increase in carbonic anhydrase activity (p < .01). Control activity was 10.9 +/- 1.2 mol CO2/(min)(mg protein X 10(-8), while carbonic anhydrase activity in fractions exposed to cholera toxin was 28.4 +/- 0.8. PGE2 had no effect, however, upon choroid plexus carbonic anhydrase activity. Since both PGE2 and cholera toxin stimulate cyclic AMP production in vitro, a compartmental model of secretory control is proposed.
mesh_terms: D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002256:Carbonic Anhydrases / Q000378:metabolism*; D002772:Cholera Toxin / Q000494:pharmacology*; D002831:Choroid Plexus / Q000201:enzymology*; D000242:Cyclic AMP / Q000096:biosynthesis; D008297:Male; D011458:Prostaglandins E / Q000494:pharmacology; D051381:Rats
chemical_list: D011458:Prostaglandins E; D003994:Bucladesine; D002772:Cholera Toxin; D000242:Cyclic AMP; D002256:Carbonic Anhydrases