title: Trypsin-induced increase in cyclic AMP concentration in rat thymocytes. An effect independent of calcium and calmodulin.
abstract: Trypsin produces a dose-related increase in cellular cyclic AMP concentration in rat thymocytes [Shneyour, Patt & Trainin (1976) J. Immunol. 117, 2143-2149; Segal & Ingbar (1983) Clin. Res. 31, 277A]. In the present study, I examined whether this effect of trypsin requires Ca2+ and whether it is modified by calmodulin. In fresh thymocytes suspended in standard medium (containing 1 mM-Ca2+), trypsin produced a concentration-dependent increase in cytoplasmic free Ca2+ concentration, which was evident at a concentration of 50 micrograms of trypsin/ml and reached maximal values at about 1 mg/ml. This effect of trypsin was very prompt in onset, almost immediate, and reached maximal values within 2-3 min. But in cells suspended in essentially Ca2+-free medium (6 nM free Ca2+), trypsin had no effect on cytoplasmic free Ca2+ concentration, which indicates that trypsin acted by increasing Ca2+ uptake rather than Ca2+ release from an intracellular pool. However, the increase in thymocyte cyclic AMP concentration produced by trypsin was independent of extracellular Ca2+ and was not influenced by calmodulin, because it was the same in the presence or absence of Ca2+ and was not changed by the calmodulin inhibitor trifluoperazine. I therefore suggest that in rat thymocytes the trypsin-induced increase in cyclic AMP concentration does not require Ca2+ and is not influenced by calmodulin.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002147:Calmodulin / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism*; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D051381:Rats; D011919:Rats, Inbred Strains; D013950:Thymus Gland / Q000187:drug effects / Q000378:metabolism*; D014268:Trifluoperazine / Q000494:pharmacology; D014357:Trypsin / Q000494:pharmacology*
chemical_list: D002147:Calmodulin; D014268:Trifluoperazine; D000242:Cyclic AMP; D014357:Trypsin; D000262:Adenylyl Cyclases; D002118:Calcium