Ergotamine alters plasma concentrations of glucagon, insulin, cortisol, and triiodothyronine in cows

Bovine plasma was assayed to determine whether ergotamine, an ergopeptide i solated from endophytic tall fescue, affected cortisol, triiodothyronine, i nsulin, and glucagon concentrations. In Exp. 1, four heifers received an i. v. bolus injection of ergotamine tartrate (19 mu g/kg BW) or saline vehicle in a simple crossover design 2 d after induced luteolysis. Oxytocin (100 U SP units) was i.v. administered 4 h after ergotamine or saline. Treatment x time affected (P < .01) respiration rates and plasma concentrations of cor tisol, triiodothyronine, insulin, and glucagon. Respiration rates were elev ated (P < .01) 2 to 7 h after ergotamine, but they were unchanged after sal ine. Plasma cortisol concentrations were increased (P < .01) 1 to 3 h after ergotamine but not after saline. Plasma triiodothyronine was elevated 2 h after ergotamine, but it was unchanged in response to saline. Insulin decre ased (P < .01) and glucagon increased (P < .01) during the 1st h after ergo tamine, but not in response to saline. A second increase (P < .01) of gluca gon was observed 3 h after ergotamine. In Exp. 2, six cows were treated wit h an i.v. bolus injection of ergotamine (20 mu g/kg BW) or saline in a simp le crossover design 10 d after receiving a s.c. ear implant containing norg estomet, Oxytocin (100 USP units) was i.v. administered 4 h after ergotamin e or saline, Treatment x time affected (P < .001) respiration rates, cortis ol, insulin, and glucagon and tended to influence (P = .12) triiodothyronin e concentrations. Respiration rates were elevated (P < .01) 1 to 7 h after ergotamine but were unaltered by saline. Plasma cortisol was elevated (P < .01) 1 to 5 h after ergotamine, but not in response to saline. Plasma triio dothyronine was elevated (P < .01) 1 to 2 h after ergotamine, but not after saline. Insulin was decreased (P < .01) and glucagon increased (P < .01) w ithin 1 h after ergotamine treatment, but they were not altered by saline. A second increase (P < .01) of glucagon occurred by 4 h after ergotamine, I n Exp. 1 and 2, glucagon increased (P < .01) 1 h after oxytocin in saline a nd ergotamine cows. Results indicate that ergotamine can alter plasma conce ntrations of hormones that mediate nutrient metabolism and thermoregulation in cattle.