Absorption, distribution, metabolism and excretion of avicatonin were investigated in male and female rats and male dogs after a single i.m. administration of 125I-avicatonin.After a single i.m. administration of 125I-avicatonin to male and female rats (2 U/kg), total and TCA precipitable radioactivity reached to a peak at 15 min and 5 min, resp., showing rapid absorption of 124I-avicatonin from administration site.TCA precipitable radioactivity was decreased more rapidly than total radioactivity and TCA soluble radioactivity was increased rapidly.High radioactivity was detected in kidney, liver, femur, bone marrow, stomach and thyroid.HPLC anal. showed that most radioactivity distributed to kidney and femur, target organs of calcitonin, was unchanged 125I-avicatonin.The unchanged 125I-avicatonin was retained even at 4 h after administration. ABS radioactivity in most tissues were reached to a peak at 15 min or 1 h and then decreased except for thyroid.In plasma, radioactive peaks to be considered as degraded fragments of 125I-avicatonin were found.Within 168 h after i.m. administration of 125I-avicatonin to male and female rats (2 U/kg), 93.6% and 92.4% of the administered radioactivity was excreted in urine, resp.Biliary excretion rate was 4.6% of the administered radioactivity within 48 h after administration of 125I-avicatonin to male rats (2 U/kg).Between male and female rats, there were no notable differences in plasma level profile, distribution and excretion after i.m. administration of 125I-avicatonin (2 U/kg).After i.m. administration of 125I-avicatonin to male dogs (10 U/kg), total and TCA precipitable radioactivity was reached to a peak at a 1 h and 20 min., resp., suggesting that absorption of 125I-avicatonin in dogs was slower than that in rats.Within 19 days after i.m. administration of 125I-avicatonin to male dogs (10 U/kg), 89.1% and 9.5% of the administered radioactivity was excreted in urine and feces, resp.
