Modulation of beta2- and beta3-adrenoceptor-mediated relaxation of rat oesophagus smooth muscle by protein kinase C.

Although a prominent role for protein kinase C (PKC) in the cross-talk between the phosphoinositide pathway and beta2-adrenoceptor signalling has been indicated, modulation of beta3-adrenoceptor function by PKC has not been studied thus far. In the present study, we have compared the relative capacity of PKC in modulating beta2- and beta3-adrenoceptor-mediated relaxation of methacholine-contracted rat oesophagus smooth muscle. To this purpose the effects of the PKC-inhibitor GF 109203X (2-[1-(3-dimethylaminopropyl)-1H-indol-3-yl]-3-(1H-indol-3-yl)-maleimide) on relaxation induced by fenoterol, formoterol, (-)-noradrenaline, BRL 35135 (4-[2-[(2-hydroxy-2-(chlorophenyl)ethyl)amino]-propyl]-phenoxyacetic-acidmethylester) and IBMX (3-isobutyl-1-methyl-xanthine) were studied, in the absence and presence of the selective beta2-adrenoceptor antagonist ICI 118,551 (erythro-1(7-methylindan-4-yloxy)-3-(isopropylamin)-butan-2-ol).

Beta-adrenoceptors mediate inhibition of lipolysis in adipocytes of tilapia (Oreochromis mossambicus).

The regulation of triglyceride mobilization by catecholamines was investigated in the teleost fish Oreochromis mossambicus (tilapia) in vivo and in vitro. In vitro experiments were carried out with adipocytes that were isolated for the first time from fish adipose tissue. For the in vivo experiments, cannulated tilapia were exposed to stepwise decreasing oxygen levels (20, 10, and 5% air saturation; 3.