Age-related changes in endogenous respiration, respiration control ratio and malonate inhibition of oxygen consumption of liver homogenate of male garden lizards

Effect of thyroxine (T4) and thiourea on the hepatic oxygen consumption of male garden lizards of three different age groups

Administration of T4 (1 microgram/g body-weight on alternate days) to male garden lizards of three different age groups (young, middle-aged and old) for a period of 2 weeks caused a significant rise in the hepatic oxygen consumption, the degree of response increasing with advancing age. On the other hand, when treated in vitro (5 micrograms T4 in the medium) the stimulation of hepatic oxygen consumption was observed only in lizards of the young age group. Oral administration of thiourea (0.05 mg/g body-weight on alternate days, three doses) led to a decrease in hepatic oxygen uptake, the degree of inhibition being higher in young (30%) and old (28%) than in middle-aged lizards (12%).