Hyperthyroid induced changes in adrenergic receptor status in guinea pig vas deferens
Ahuja, G.B.; Goyal, R.K.; Verma, S.C.
Indian Journal of Experimental Biology 21(5): 272-274
1983
ISSN/ISBN: 0019-5189 PMID: 6667979 Document Number: 207996
Noradrenaline and phenylephrine, produced dose-dependent contractions in the vasa-deferentia obtained from normal (euthyroid) and hyperthyroid (induced by chronic administration of tri-iodo-l-thyronine-sodium) guinea pigs. The responses were competitively blocked by phentolamine (1.0 .times. 10-7 M). The contractile response of noradrenaline and phenylephrine and the degree of blockade by phentolamine were significantly diminished on thyronine pre-treatment of guinea pigs. In the depolarized vasa deferentia, isoprenaline produced dose-dependent relaxation in euthyroid and hyperthyroid states. The relaxations were more prominent during the hyperthyroid state. Phentolamine (1.0 .times. 10-7 M) potentiated and propranolol (10-6 M) inhibited competitively the responses to isoprenaline. The inhibitory potency of propranolol was greater in tissues from hyperthyroid animals. An increase in .beta.-adrenoceptor activity and simultaneous decrease in .alpha.-adrenoceptor activity in the hyperthyroid state is suggested.