Hypoxic cardiac hypertrophy is not inhibited by cardioselective or non-selective beta-adrenoceptor antagonists.

1. Young rabbits, eight at a time, were exposed to more than 170 hr of hypoxia (O2 at 70-80 torr) at atmospheric pressure during 9-11 days. 2. The animals were injected twice daily with doses of beta-blockers up to the highest used in human therapy, or with an equivalent volume of saline. These controls were litter mates of the treated rabbits. 3. In comparison with untreated normoxic rabbits of similar age, the hypoxia induced highly significant mean increases in right ventricular dry weight (+57%, controls; +55% treated). 4. In each group, the same degree of hypertrophy was induced in the treated and control animals, irrespective of whether the drug used was a non-selective beta-blocker (propranolol) or a cardioselective drug (atenolol). 5. The right atria were also hypertrophied, though not as much as the right ventricles. 6. In all the hypertrophied tissues the water content was increased. 7. No significant change was observed in the dry weight or water content of the left ventricles of treated or control animals.