EXTRAPULMONARY BETA(2)-RESPONSES TO INTRAVENOUS SALBUTAMOL DURING THEMENSTRUAL-CYCLE

Extrapulmonary beta(2)-adrenoceptor mediated responses to salbutamol w ere evaluated in 9 healthy female subjects during the follicular (day 2-4, Visit 1) and luteal (day 21-23, Visit 2) phases of the menstrual cycle, and were compared with those of 9 age-matched male controls. At each visit, salbutamol was given by intravenous infusion for 30 minut es at a dose of 0.2 mg.kg(-1).min(-1). Plasma salbutamol concentration and responses in heart rate (HR), finger tremor (Tr), Q-T interval (Q -Tc), serum potassium (K), serum insulin (Ins) and serum glucose (Glu) were measured at baseline and at 10, 20 and 30 minutes after commenci ng the infusion. Comparisons were made between sexes and between visit s for peak responses calculated as percentage change from baseline. Me an plasma salbutamol concentration (ng.ml(-1)) were not significantly different between males and females on Visit 1: 6.9 (95% CI 6.01, 7.82 ) vs 7.3 (95% CI 6.4, 8.3), or on Visit 2: 6.9 (95% CI 6.0, 7.8) vs 7. 2 (95% CI 6.3, 8.1). On Visit 1, significantly greater responses were demonstrated in females, compared with males for K (as mean difference ): 6 (95% CI 1, 11) %, Tr: 17 (95% CI 1, 33) %, Q-Tc: 8 (95% CI 2, 14) % and Ins: 276 (95% CI 71, 481) %. In addition, a significantly great er response was demonstrated in females on Visit 1 compared with males on Visit 2 for HR (as mean difference): 32 (95% CI 1, 63) %, and for Ins: 262 (95% CI 57, 467) %. Thus, despite no difference in plasma sal butamol concentrations, female subjects exhibited greater responsivene ss to salbutamol compared with males during the follicular phase of th e menstrual cycle. This suggests that in vivo, females have enhanced s ensitivity of extrapulmonary beta(2)-adrenoceptors.