Effect of ovulation on haem metabolism in rabbits

To investigate the origin of the cyclic changes in the rate of endogenous carbon-monoxide production (nCO) during the menstrual cycle, haem turnover was determined before and after chorion gonadotropic hormone-induced ovulation in six female rabbits. 14C-labelled delta-aminolevulinic acid and glycine were administered and the excretion rate of 14CO (A14CO) was measured for determination of hepatic and bone-marrow haem turnover, respectively. Carbon-monoxide production (nCO) was measured to estimate total haem turnover. After ovulation A14CO was increased significantly the first 2 h of the early labelled peak after 14C-ALA administration and was increased also at the first determination during the early peak after 14C-glycine but statistically not significantly. The total excretion of labelled CO during the period of the early labelled peak was not increased with any of these precursors for haem synthesis. On the other hand nCO was increased 34% (P less than 0.05) during the post-ovulation period. As the increase in 'unassigned' haem turnover was small and may be unaccompanied by a contemporary increase in bilirubin/CO production, it was concluded that the increase in nCO during the post-ovulation period essentially depends on increased destruction of circulating red cells in the rabbit.