EFFECT OF ERGOTAMINE AND ERGONOVINE ON THE BOVINE LIVER MITOCHONDRIALATPASE SYSTEM

This study was conducted to determine the effects of selected ergot al kaloids on mitochondrial ATPase activity in bovine liver. We determine d the actions of ergonovine and ergotamine on Ca2+ dependent ATPase in vitro using whole liver homogenate and a mitochondrial membrane prepa ration. Data were collected in triplicate from three different prepara tions on three different dates. Ergotamine caused a dose-dependent inh ibition of Ca2+ activated ATPase activity. Ergonovine inhibited Ca2+ a ctivated ATPase to a lesser degree as compared with ergotamine. Kineti c data from a Lineweaver-Burk plot of 1/V versus 1/S showed that the i nteraction between ergotamine or ergonovine and Ca2+ ATPase was a non- competitive inhibition with decreased V-max (2.41, 0.84, and 0.54 for control, ergonovine and ergotamine, respectively) in the presence of e rgotamine or ergonovine. The K-m values were 1.54, 1.08 and 1.11 for c ontrol, ergonovine, and ergotamine, respectively. This work provides i nformation on the interaction of ergot alkaloids with liver mitochondr ial ATPase, which is of importance in understanding the involvement of liver mitochondria in the changes in energy metabolism associated wit h fescue toxicoses. (C) 1998 Lippincott Williams & Wilkins.