Effects of beta-adrenergic antagonists (carvedilol and propranolol) on beta 2-adrenergic receptors and factor VIII levels in hyperthyroid cats

Abstract

The objective of this study was to compare effects of [beta][subscript 2] adrenergic blockers (carvedilol and propranolol) on factor VIII levels and [beta][subscript 2] adrenergic receptors in normal and hyperthyroid cats. Twelve cats were divided into two groups, a control group (n = 4) and a hyperthyroid group (n = 8), which animals in the hyperthyroid group were given L-thyroxine at the dose of 50 microgram/kg/day for 14 days. After an induction period, all animals were randomly selected to treat first with either propranolol or carvedilol. Half of animals received orally 1 mg/kg/day of propranolol combination with L-thyroxine once daily for a total period of 14 days. After that, animals were allowed to rest and washout for 14 days, and then they were received L-thyroxine for 14 days followed by L-thyroxine combination with 1 mg/kg/day carvedilol once daily for 14 days. Another half received carbedilol; then followed by propranolol. Blood samples were drawn for determinations of thyoxine levels, factor VIII levels, prothrombin time (PT), activated partial thromboplastin time (APTT), and [beta][subscript 2] adrenergic receptor density. It was found that the hyperthyroid animals shown an increase in factor VIII levels. Carvedilol decreased thyroxine and factor VIII levels, but propranolol decreased only thyroxine levels. There was no change on the density of [beta][subscript 2] adrenergic receptors after thyroxine induction and after treated with either carvedilol or propranolol. These results indicate that factor VIII, which is related to thromboembolism, can be decreased by carvedilol.