Plasma Growth Hormone Concentrations in Sheep Measured by Radioimmunoassay

Responses to exogenous growth hormone were measured in lactating dairy cows surgically prepared to allow measurement of nutrient exchanges across mammary and hind-limb muscle tissues. Cows were injected daily with either saline or growth hormone, at a dose of 0·1 mg/kg liveweight, over periods of 6 days.During administration of growth hormone milk yield, milk fat content and yields of milk fat protein and lactose increased. Arterial plasma concentrations of glucose and non-esterified fatty acids were increased, uptake of glucose by leg muscle tissue decreased, lactate release from leg muscle tended to increase, mammary uptake of non-esterified fatty acids increased, blood flow to leg muscle tended to increase and blood flow to mammary tissue increased during injection of growth hormone.The results show that growth hormone affects supply to and utilization of key nutrients by tissues, resulting in the supply to the mammary gland of additional precursors for milk synthesis.

Section: Hormone Assaysmentioning

confidence: 99%

Effects of Exogenous Growth Hormone on Milk Production and Nutrient Uptake by Muscle and Mammary Tissues of Dairy Cows in Mid-lactation

McDowell¹,

Gooden²,

Leenanuruksa³

et al. 1987

“…Plasma glucose was determined by the glucose oxidase method of Huggett and Nixon (1957); free fatty acids (FFA) by the method of Dole (1956), as modified by Annison (1960); and insulin and growth hormone by radio-immunoassay using talc to separate antibody-bound and free hormone (Rosselin et al 1966;Wallace and Bassett 1970). Sodium and potassium were determined by flame-photometry with an autoanalyser (Technicon Instruments Corp. N.Y.) and urea was determined on an autoanalyser by the method of Wilson (1966).…”

Section: (D) Analyticalmentioning

confidence: 99%

“…Plasma concentrations of FF A, insulin, and growth hormone were transformed to logarithms (base 10) before calculation of means (Patterson et al 1964;Welborn et al 1966;Wallace and Bassett 1970). For clarity, antilogs of means are used in the presentation of results.…”

Section: (D) Analyticalmentioning

confidence: 99%

“…Possibly there was also a very small increase in plasma glucose during the infusion of 0·05 /Lg glucagon/min, but there was no increase in insulin with either this or the smallest rate of infusion (0· 01 /Lg/min) used. To compare the potency of glucagon and adrenaline as agents increasing the plasma glucose of sheep, the incre-ments in plasma glucose during the first 30 min of glucagon and adrenaline infusion have been compared with those observed in another group of sheep given infusions of adrenaline at a variety of rates (Bassett 1970). The increment in glucose was clearly related to loglo of the glucagon infusion rate (Fig.…”

Section: (A) Plasma Glucose and Insulinmentioning

confidence: 99%

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The Effects of Glucagon on Plasma Concentrations of Insulin. Growth Hormone, Glucose and Free Fatty Acids in Sheep: Comparison with the Effects of Catecholamines

Bassett¹

1971

Glucagon, adrenaline, and isoprenaline were administered to adult sheep by intravenous infusion at a rate of 5 p.g/min for 2 hr.Plasma glucose concentration increased more rapidly during glucagon infusion than during infusion of either adrenaline or isoprenaline.Plasma insulin concentration increased rapidly during glucagon infusion, but the increase was less than that observed during infusion of isoprenaline. There was almost no increase in plasma insulin during infusion of adrenaline despite marked hyperglycaemia.Plasma growth hormone concentration increased during glucagon infusion, but high levels were not maintained. Both adrenaline and isoprenaline decreased growth hormone concentration.Plasma free fatty acid concentrations decreased during glucagon infusion. Plasma sodium and potassium concentrations also decreased but the plasma concentration of urea nitrogen was not altered during glucagon infusion.Intravenous infusion of glucagon at rates of 0·5 and O· 1 p.g/min for 2 hr also significantly increased plasma glucose, insulin, and growth hormone concentration and decreased plasma free fatty acid concentration. Infusion of glucagon at lower rates (0·05 and 0·01 p.g/min) had no significant effects.

“…The talc radioimmunoassay described by Wallace and Bassett (1970) was used. Antiserum specific for ovine growth hormone was obtained from Mr A. L. C. Wallace, Division of Animal Production, CSIRO, Prospect, N.S.W.…”

Section: Growth Hormonementioning

confidence: 99%

Control of Gluconeogenesis in the Lactating Sheep

Gow¹,

McDowell²,

Annison³

1981

Aust. J. Bioi. Sci. 1981, 34, 469-78 Ewes which had been lactating for 3-4 weeks and which had been milked by hand from the day of parturition were subjected to food restriction for 4 days. One group of three ewes was fed ad libitum and a second group of four ewes was fed to meet calculated requirements for maintenance and milk production. Over 4 days food intake was reduced by 80 % in both groups of ewes.In response to food restriction, milk yields and body weight decreased. Blood amino acids, plasma glucose, glucose pool size, glucose irreversible loss, insulin, thyroxine and the insulin: glucagon molar ratio decreased. In contrast, plasma glucagon remained relatively unaffected and plasma free fatty acids and growth hormone increased. These changes were similar for both groups of ewes and were reversed when food intake was restored.The results suggest that the hormonal control of gluconeogenesis in the ruminant is similar to that in the non-ruminant.