Acute and subacute metabolic and endocrine effects of clenbuterol in female pigs.

The aim of the study was to assess the relationship between acute and subacute metabolic and endocrine effects after intravenous administration of the beta2-adrenergic agonist clenbuterol in a growth-promoting dose to female pigs. Acute metabolic and endocrine effects were assessed by measuring the blood glucose, serum insulin and nonesterified fatty acid (NEFA) concentrations during 300 min after a single administration of clenbuterol. Significantly higher serum insulin and NEFA concentrations (19.90 +/- 2.50 microU/ml, p<0.01, and 0.69 +/- 0.04 mmol/L, p<0.001, respectively) were measured 30 min after the preprandial administration of clenbuterol in female pigs. Over the same period, the levels of blood glucose (4.42 +/- 0.30 mmol/L) showed no difference from those of control pigs. The postprandial serum NEFA concentration decreased moderately during 210 min after feeding. Postprandial blood glucose and insulin concentrations increased and reached maximal levels 120 min after clenbuterol administration (10.91 +/- 0.60 mmol/L and 85.22 +/- 7.24 microU/ml, respectively), and returned to basal levels at 300 min (4.20 +/- 0.21 mmol/L and 7.75 +/- 1.60 microU/ml, respectively) after the administration of clenbuterol. Subacute metabolic and endocrine effects were assessed by measuring the blood glucose, serum insulin and NEFA concentrations for 21 days after the repeated doses of clenbuterol. In addition, the influence of clenbuterol administration on the endocrine regulation of the onset of the next expected oestrus in female pigs was assessed by measuring their serum 17beta-oestradiol and progesterone concentrations. Blood glucose, serum insulin and NEFA concentrations after the last administration of clenbuterol did not differ significantly from those in control animals. The onset of the next expected oestrus occurred regularly without any significant difference in serum 17beta-oestradiol or progesterone concentrations between the treated (9.83 +/- 2.60 pg/ml and 0.15 +/- 0.03 ng/ml) and control pigs (8.52 +/- 2.70 pg/ml and 0.25 +/- 0.06 ng/ml). The study results suggest the duration of intravenous administration of clenbuterol in a growth-promoting dose necessary to influence the metabolic and endocrine activities in female pigs.