Influence of two beta-adrenoceptor antagonists, propranolol and pindolol, on cold adaptation in the rat.

1. Adult male rats were treated with propranolol (2.0 mg kg-1 day-1 i.p.), pindolol (0.2 mg kg-1 day-1 i.p.) or 0.9% NaCl day-1 i.p. and exposed to +4 degrees C for 42 days, or treated with 0.9% NaCl day-1 i.p. and kept at +23 degrees C for 42 days. They were weighed once a week, when a 24 h urine sample was also collected and colon temperature measured. 2. Urinary noradrenaline (NA), adrenaline (Ad) and dopamine were analysed by high-performance liquid chromatography with an electrochemical detector. After the acclimatization period the interscapular brown adipose tissue was excised and weighed and the activity of the oxidative enzymes succinate dehydrogenase and cytochrome oxidase measured. 3. The pindolol-treated and propranolol-treated rats gained weight during the cold-acclimatization period. The amount of interscapular brown adipose tissue increased in the cold, but the increase was lowest in the pindolol-treated group. No changes were seen in the other brown adipose tissue parameters in cold-exposed animals. The excretion of catecholamines followed the same pattern in all three cold-exposed groups, with an initial rise in noradrenaline and adrenaline excretion and a slight rise in dopamine excretion. 4. The results suggest possible connections between beta-adrenoceptor antagonists, weight gain and cold acclimatization. Pindolol had a slight inhibitory effect on cold-induced brown adipose tissue hypertrophy in rats.