Effect of atropine on plasma amino acid levels and milk secretion of cows.
Subcutaneous injections of 30 mg atropine into lactating cows induced a 20--40% decrease of free amino acid (AA) levels in arterial plasma. Minimum levels were observed after 30--50 min. The decline persisted for more than 6 h. The greatest fall in concentration was noted for tyrosine, methionine, lysine, arginine, phenylalanine and threonine. Arterial glucose levels remained unaffected. The effect of atropine on milk secretion was studied in 2 cows which were milked every hour with the aid of oxytocin. Maximal effects were observed after 3--4 h. They included reduction in concentration of casein and alpha-lactalbumin (alpha-la) and a decline in production of milk (20%), casein (35%), alpha-la (45%) and lactose (18%). Uptake by the lactating udder over a period of about 1 h after injection of atropine was studied in 2 cows. Mammary blood flow and glucose uptake remained unaffected. There was a positive correlation between arteriovenous differences of essential AA and arterial plasma concentrations. The uptake of essential AA decreased by approximately 50%. There was no evidence that atropine has a direct inhibiting effect on the udder. It is suggested that the decrease of alpha-la synthesis might induce an inhibition of lactose synthesis and milk production.
D000596:Amino Acids / Q000097:blood* / Q000378:metabolism; D000818:Animals; D001285:Atropine / Q000494:pharmacology*; D002417:Cattle / Q000378:metabolism*; D005260:Female; D007774:Lactation / Q000187:drug effects*; D008321:Mammary Glands, Animal / Q000187:drug effects* / Q000378:metabolism; D011247:Pregnancy; D012965:Sodium Chloride / Q000494:pharmacology
D000596:Amino Acids; D012965:Sodium Chloride; D001285:Atropine