Effects of clonidine on glucose production and insulin secretion of cattle.

Clonidine-2-(2,6-dichlorophenylamine)-2-imidazoline hydrochloride, a potent alpha-adrenoceptor stimulant, was given to dairy heifers. Administration of either 2 or 20 microgram of drug/kg during 10 minutes resulted in decreased immunoreactive serum insulin (IRI) concentrations and increased serum glucose concentrations 5 minutes after administration. Drug administration resulted in a protracted decrease (P less than 0.01) of serum IRI and a protracted increase (P less than 0.01) in serum glucose. Doses differed significantly (P less than 0.01) with regard to their ability to alter IRI and glucose concentrations. Clonidine also significantly (P less than 0.05) enhanced glucose release from liver slices of heifers in vitro. Clonidine stimulated cyclic 3'5' adenosine monophosphate (cAMP) production in liver tissue slices when they were incubated in the presence (or absence) of theophylline, indicating that the mechanisms bringing about changes in liver glucose release and cAMP production were related.