Biomedical subjects

R W Rosebrough

Publications and source records attributed to R W Rosebrough.

At least 37 records · Page 2Linked to original sources

PubMed1998

Assessment of developmental changes in chicken and turkey insulin-like growth factor-II by homologous radioimmunoassay.

The development of a homologous RIA for chicken insulin-like growth factor-II (cIGF-II) and its application to investigate the developmental changes in IGF-II in the chicken and turkey are described. A double-antibody RIA has been developed using recombinantly derived cIGF-II as antigen, radiolabelled tracer and standard. Serial dilutions of chicken and turkey plasma were parallel to serial dilutions of cIGF-II standard. We have also established that acid/ethanol extraction of chicken and turkey plasma reduced possible interference of insulin-like growth factor-binding proteins in the RIA. Consumption of a low-protein diet by male chickens lowered plasma IGF-I twofold, whereas IGF-II levels were unchanged. Food withdrawal evoked an increase in circulating IGF-II, while IGF-I levels were reduced. Refeeding returned both growth factors to normal circulating concentrations. During chick embryo incubation, plasma IGF-II levels were tenfold higher than those of IGF-I. In the turkey embryo, plasma IGF-II concentrations were higher than those of IGF-I. During the post-hatch period. IGF-II levels declined with age in chickens. In the growing turkey, IGF-II levels were consistently higher than IGF-I levels. The application of the homologous RIA to monitor plasma levels during embryonic development and post-hatch growth in avian species will provide more accurate comparisons of results from studies on the role of IGF-II in growth and metabolism of domestic birds.

Animals↗

PubMed1998

Porcine somatotropin, dietary protein and energy effects on arginase and transaminase activities in pigs.

Two experiments were conducted with cross-bred barrows to determine the effect of somatotropin administration on liver enzyme activities. In the first experiment, pigs growing from 26 to 55 kg body weight were given two doses of pituitary porcine somatotropin (pST; 0 and 100 micrograms per kg body weight) and three levels of dietary energy (60, 80 and 100% of free choice intake). In the second experiment, pigs growing from 30 to 60 kg body weight were given two doses of recombinant porcine somatotropin (rpST; 0 and 100 micrograms per kg body weight) and five levels of dietary crude protein (110, 150, 190, 230 and 270 g crude protein/kg diet). Liver arginase (ARG, EC 3.5.3.1) and aspartate aminotransferase (AAT, EC 2.6.1.1) activities were then determined in organ samples taken at slaughter time. Dietary energy did not change liver ARG. Activities of both ARG and AAT increased as dietary crude protein increased. Both pST and rpST decreased ARG, AAT and serum utrea nitrogen. There was a lack of interaction between rpST therapy and dietary protein on either ARG or AAT activities, suggesting that set nutritional states are not required for expression of pST effects.

Animal Nutritional Physiological Phenomena↗

PubMed1997

Body composition analysis of chickens by dual energy x-ray absorptiometry.

Dual-energy x-ray absorptiometry (DXA) was evaluated as a method for measuring the body composition of growing broiler chickens. A total of 130 chickens, ranging in weight from 400 to 3,290 g, were scanned using a DXA instrument (Lunar DPX-L). Single whole-body scans were acquired and analyzed using pediatric total body research software (neonatal mode) or small animal total body research software (detail or high resolution mode). The DXA measurements provided readings of total tissue mass, percentage fat, fat tissue mass, lean tissue mass, and bone mineral content. After scanning, the bodies of the chickens were frozen, then, after removing the feathers, homogenized for chemical determination of fat, water, and protein content. By chemical analysis, the whole body fat content of the chickens ranged from 2.8 to 27.2%, giving rise to DXA R values (ratio of attenuation coefficients) ranging from 1.415 to 1.339. The accuracy of DXA for measuring total body fat was a function of the scanning program and mode and also the size of the bird. The best agreement between DXA and chemical measurements of percentage body fat were obtained when chickens weighing more than 2,000 g were scanned using either the small animal-detail mode or neonatal mode. None of the scan modes proved to be accurate for measuring the fat content of birds weighing less than 2,000 g. The DXA measurement of lean mass of chickens was found to be highly correlated with both total body protein (R2 = 0.90) and total body water (R2 = 0.93), but was of little value for predicting percentage values for either. The ratio of DXA bone mineral content to total body ash was 0.77; however, the correlation (R2) between the two was only 0.46. These results suggest that although the DXA technique is potentially useful for measuring body composition of chickens, considerable refinement is needed prior to routine application.

Absorptiometry, Photon↗

PubMed1996

Hormonal and nutritional modulation of hepatic arginase activity in growing cattle.

The hormonal and nutritional modulation of hepatic arginase activity (HARG) was characterized in growing cattle in two studies. In the first study, 20 steers (initial weight, 182 +/- 2 kg) were assigned in equal numbers to either Synovex-S (SYN) (ear implant), recombinant bovine somatotropin (Somavubove; SbV; 0.1 mg/kg intramuscularly daily), SYN + SbV, or nothing (control). Steers were individually fed, for 56 d, a concentrate (80% diet dry matter [DM]) and silage (20% diet DM) diet providing 20 g of crude protein (CP) and 252 kcal metabolizable energy (ME) per kg body weight0.75. On Day 57, samples of liver were obtained at slaughter and subsequently assayed for HARG by the incubation of a tissue homogenate for 2 hr with 250 mM arginine, with and without Mn2+ and heat activation, and the measurement of the resulting urea. HARG was uniformly increased by divalent cation (Mn2+) and heating. SYN had no effect on HARG, whereas SbV treatment resulted in an overall 34% decrease in HARG. Plasma urea nitrogen (PUN) was decreased by SbV but not consistently affected by SYN. In the second study, 16 steers (avg. initial weight, 284 +/- 5 kg) were initially fed a concentrate basal diet consisting of 11% CP and 1.96 Mcal ME for 21 d. Steers were then assigned to one of four dietary treatments (6.4 kg DM/hr per day) in a factorial arrangement of high and low CP (8 and 14%) and two levels of energy (1.96 and 2.67 Mcal ME/kg of diet DM) for 210 d and slaughtered. HARG and PUN were higher in steers fed 14% CP but were lower at each level of CP fed at the higher level of ME. The data suggest that hormonal repartitioning compounds and diet composition may modulate nitrogen metabolism by affecting the activity of arginase in the liver as well as by affecting the total content of arginase in association with changes in organ size.

Animal Nutritional Physiological Phenomena↗

PubMed1996

Crude protein and supplemental dietary tryptophan effects on growth and tissue neurotransmitter levels in the broiler chicken.

Indian River male broiler chickens growing from 7 to 28 d of age were fed on diets containing 120, 210 and 300 g crude protein/kg diet and 0, 1.67 or 16.7 g added tryptophan (TRP)/kg diet. The hypothesis tested was that crude protein levels and TRP would affect both growth and neurotransmitter metabolism. Heart, brain and pancreatic neurotransmitter (noradrenaline (NA), dopamine (DA), serotonin (5-HT) and 5-hydroxy-indole-3-acetic acid (5-HIAA)) concentrations were determined by HPLC separation and electrochemical detection. Malate dehydrogenase (2-oxoglutarate decarboxylating) (NADP+) (MDH(NADP+); EC 1.1.1.40), isocitrate dehydrogenase (NADP+) (ICD(NADP+); EC 1.1.1.42) and aspartate aminotransferase (AAT; EC 2.6.1.1) activities were also measured. Supplemental TRP decreased growth and feed intake. Increasing dietary crude protein decreased MDH(NADP+), but increased (ICD(NADP+) and AAT activities. Additional dietary TRP decreased MDH(NADP+) activity, but had no effect on other enzyme activities. Cardiac NA concentrations were directly related to dietary crude protein levels while pancreatic levels were inversely related. An increase in dietary crude protein decreased both brain NA and DA. Supplemental dietary TRP increased both 5-HIAA and 5-HT. Changes in feed intake caused by different levels of both dietary crude protein and TRP are accompanied by altered levels of neurotransmitters. The present study indicates that much larger amounts of TRP are required to make simultaneous changes in feed intake and neurotransmitters.

Animals↗

PubMed1996

Carry-over effects of dietary crude protein and triiodothyronine (T3) in broiler chickens.

Indian River male broiler chickens growing from 7 to 30 d of age were fed on diets containing crude protein levels ranging from 120 to 300 g/kg plus 0 or 1 mg triiodothyronine (T3)/kg diet. The purpose of this study was to examine the effects of these treatments on lipogenesis after a common diet was fed (180 g crude protein/kg diet from 30 to 56 d of age). Dietary treatment groups were sampled at 30 and 56 d. In vitro lipogenesis was determined by incubating liver explants for 2 h at 37 degrees in Hanks' salts containing 25 mM-HEPES and 10 mM-[2-14C]acetate and then measuring acetate incorporation into total lipid. Growth and feed consumption from 7 to 30 d increased (P < 0.01) as dietary protein increased from 120 to 210 g/kg diet. Both measurements decreased as crude protein increased from 210 to 300 g/kg diet. T3 decreased (P < 0.01) growth and feed intake during this period. Low-protein (< 180 g/kg) diets increased (P < 0.05) and T3 decreased lipogenesis in 30-d-old chickens. Although birds given T3 from 7 to 30 d grew at the greatest rate from 30 to 56 d of age, the final body weight was still less than controls. In vitro lipogenesis at 56 d of age was not affected by either of the two dietary treatments. In contrast, the relative size of the abdominal fat pad (g/kg body weight) at 56 d was decreased by feeding T3 from 7 to 30 d. Any changes in metabolism elicited by either dietary protein levels or hormone treatments may be specific to the particular dosing interval and are not sustained when a common diet is fed during a repletion period.

Adipose Tissue↗

PubMed1996

Dietary crude protein changes rapidly alter metabolism and plasma insulin-like growth factor I concentrations in broiler chickens.

Although changes in dietary crude protein levels change metabolism in broiler chickens, there is little information concerning the time course of the process of adaptation. Therefore, male Indian River broiler chickens were fed diets containing either 120 or 210 g protein/kg from 7 to 28 d of age and then were fed the other level for an additional 12 d. Birds were bled and killed at 0, 2, 5, 7, 9 and 12 d following the reversals. Measurements taken at these intervals included in vitro lipogenesis, growth and feed consumption, hepatic enzyme activities and plasma metabolites and metabolites. Birds fed the lower level of crude protein were smaller and less efficient in growth from 7 to 28 d. Feeding these birds a higher protein diet from 28 to 40 d improved both growth and feed efficiency. Lipogenesis was also greater and plasma insulin-like growth factor-I (IGF-I) less in birds fed the lower protein diet. Switching dietary treatments increased and decreased lipogenesis as birds were switched from high to low protein and from low to high protein diets, respectively. Half-maximal changes were observed 4 d after the reversal and maximal changes 7 d after the reversal. In contrast, switching dietary treatments decreased and increased plasma IGF-I as birds were switched from high to low protein and from low to high protein diets, respectively. Half-maximal changes were observed 2 d after the reversal. Of the three hepatic enzymes monitored, malic enzyme activity most closely followed the rapid changes in in vitro lipogenesis. Plasma IGF-I may be a more sensitive indicator of changes in dietary protein than changes in intermediary metabolisms.

Aging↗

PubMed1995

Effect of dietary energy intake and exogenous porcine growth hormone administration on circulating porcine growth hormone concentration and response to human growth hormone-releasing factor administration in growing swine.

In a 2 x 2 treatment array (n = 4 pigs/treatment), the effects of feed intake (ad libitum vs. restricted to 60% ad libitum) and the daily administration of excipient buffer or porcine pituitary-derived growth hormone (GH) at a dose of 100 micrograms/kg body weight per day on serum GH profile and human growth hormone-releasing factor (hGRF) response were examined in barrows weighing 55 kg. Feed intake treatment was implemented from 25 to 55 kg live weight. Buffer or GH treatment was implemented for 10 d before sampling. After GH treatment, the integrated serum GH concentration area was 25% greater in barrows fed restrictively. Data are consistent with the suggestion that GH dose to improve the efficiency of lean tissue deposition be adjusted according to feeding regimen. The serum GH response to hGRF was also altered by level of feed intake. The ad libitum feeding of buffer-treated animals resulted in a monophasic serum GH response to hGRF, whereas barrows fed restrictively had a biphasic response to hGRF. Together, these data suggest that feed intake pattern alters GH secretion and as such could influence the practical implementation of somatotropin as a metabolism modifier in swine.

Animals↗

PubMed1995

Tissue IGF-I protein and mRNA responses to a single injection of somatotropin.

Swine were divided into four groups of 11 animals at 40 kg body wt. Swine within a group were given a single porcine somatotropin (pST) injection (200 micrograms/kg) or buffer at 0800. Blood, liver (L), latissimus dorsi (LD), semitendinosus (STS), vastus lateralis (VL), dorsal subcutaneous (SQ), and perirenal (PR) adipose tissues were sampled at 0, 1, 2, 4, 8, 12, 16, and 24 h postinjection. Blood urea nitrogen was depressed by 16 h. Insulin was elevated by approximately 350% at 8 h. Lipogenic enzyme activities in adipose tissues were not affected by pST treatment. Insulin-like growth factor I (IGF-I) mRNA levels increased rapidly in SQ, PR, and L to a single pST administration, whereas they increased only slightly in VL. IGF-I mRNA concentrations in LD and STS were unaffected by pST treatment. IGF-I protein content of tissues changed little during the first 24 h postinjection. These data suggest that individual tissues differ in timing and degree of response to pST. Conflicting results reported after pST treatment could, in part, be due to tissue selection for sampling or sample timing.

Adipose Tissue↗

PubMed1995

Protein and energy relationships in the broiler chicken. 12. Dietary protein and triiodothyronine (T3) effects on the response of broilers to isoproterenol and cyclic adenosine monophosphate in vitro.

Indian River male broiler chickens (7-d-old) were fed on diets containing 120, 210 or 300 g crude protein/kg + 0 or 1 mg triiodothyronine (T3)/kg diet (Expt 1) and 120, 150, 180 or 210 g crude protein/kg + 0 or 1 mg T3/kg diet (Expt 2) to determine the effects of crude protein level and T3 on growth and metabolism. Body composition of chickens was determined by a combination of dissection of muscle and abdominal fat pads, and chemical extraction (Expt 1). In vitro lipogenesis (IVL) was determined in both experiments by incubating liver explants for 2 h at 37 degrees in the presence of 10(-4) M-dibutyryl cyclic AMP (cAMP) or 10(-5) M isoproterenol (ISO) and 10(-2) M-[2-14C]acetate. Acetate incorporation into total lipid was an indication of IVL. Activity ratios for each of these additions relative to control (-cAMP-ISO) were calculated to ascertain basal v. inhibited rates of IVL. The relative muscle mass was increased by increasing crude protein from 120 to 210 g/kg diet but not from 210 to 300 g/kg diet. Dietary T3 decreased total body lipid regardless of the dietary crude-protein level. Increasing dietary crude protein decreased (P < 0.05) basal IVL (-cAMP-ISO) but not IVL (+cAMP). Dietary T3 decreased basal IVL in birds fed on the diets containing 120 and 210 g crude protein/kg but had little effect on the two inhibited states of lipogenesis (+cAMP or +ISO). The component of lipogenesis sensitive to in vitro inhibition is also the component under dietary control.

Acetates↗

PubMed1994

Nutritional effects on neurotransmitter metabolism in the broiler chicken.

Two experiments were conducted with broiler chickens to determine various nutritional effects on neurotransmitter metabolism. In Experiment 1, 21-day old chickens were fasted for 24 hr, fed on an ad libitum basis, fed a diet containing 450 g crude protein/kg (high-protein) or fed a diet containing 80 g crude protein/kg (high carbohydrate) to examine nutritional regimens that may alter neural factors regulating growth. Chickens were injected (250 mg/kg BWt) with a tyrosine hydroxylase inhibitor, alpha-methyl-DL-p-tyrosine (AMPT), to inhibit catecholamine synthesis and to estimate turnover constants as functions of these treatments. In Experiment 2, 7-day old chickens were fed diets containing 120, 180, 240, and 300 g crude protein and 1 mg T3/kg diet for 21 days to determine the effects of both dietary protein and thyroid status on catecholamine concentrations. Norepinephrine (NE) and dopamine (DA) in the brains and NE and DA in the hearts and pancreases were separated by HPLC and determined by electrochemical detection. Fractional turnover of DA in the brains of both fed and fasted chickens was equal but was over twice as great as that of NE. Fractional NE turnover in hearts of both fed and fasted chickens was 12.3%/hr although fractional NE turnover in pancreas was greater (P < 0.05) in fasted than in fed chickens (9.0%/hr vs 5.1%/hr). These same rate constants were also seen in brains of chickens fed high-carbohydrate or high-protein diets. In contrast, a protein diet increase pancreatic and cardiac NE turnover compare to a high-carbohydrate diet.

Animal Nutritional Physiological Phenomena↗

PubMed1994

In vitro regulation of lipogenesis in turkey liver explants.

A mechanical tissue chopper was used to obtain liver explants (35-75 mg) from 2-3-week old turkeys to determine both tissue sensitivity and metabolic effects of adrenergic agonists (isoproterenol, propranolol, norepinephrine and phenoxybenzamine). A previously noted catecholamine induced decrease in in vitro lipogenesis in chicken liver explants was also noted in turkey liver explants. Thus, one set of control points for in vitro regulation is under control of the cAMP system. Preincubation of slices (1 hr) with propranolol blocked the inhibition of lipogenesis caused by alpha and beta-adrenergic agonists (arterenol or isoproterenol) during a subsequent 1-hr incubation. Preincubation of slices with either of these agonists decreased lipogenesis even following an extensive washout. Inhibition could be overcome with propranolol, a beta adrenergic antagonist.

Animals↗

PubMed1993

In vitro substrate utilization for lipid synthesis in liver explants from hyperthyroid chickens.

1. Indian River male broiler chickens growing from 7 to 28 days of age were fed diets containing 12, 18, 24 and 30% protein + 0 or 1 mg triiodothyronine (T3)/kg of diet to study energetic costs of lipogenesis and the use of various substrates for in vitro lipogenesis. 2. De novo lipid and CO2 production were determined in the presence of [1-14C]pyruvate, [2-14C]pyruvate, [3-14C]pyruvate, [2-14C]acetate and [U-14C]alanine. 3. Oxygen consumption was determined in mitochondrial preparations to estimate the energetic costs in explants synthesizing lipid. 4. Radiolabeled CO2 derived from [1-14C]pyruvate was used as an estimate of coenzyme A availability in liver explants. Lipids derived from [2-14C]pyruvate, [2-14C]acetate and [U-14C]alanine estimate relative substrate efficiency. 5. Labeled CO2 production from [1-14C]pyruvate was greatest in that group fed a 12% protein diet and least in the group fed a 30% protein diet. 6. In addition, T3 increased CO2 production from [1-14C]pyruvate. 7. The production of 14CO2 from the second carbon of pyruvate or acetate was increased by T3. 8. The low-protein diet (12% protein) increased (P < 0.05) lipogenesis. 9. Adding T3 to the diets decreased carbon flux into lipid from all substrates, but increased CO2 production from all substrates without changing stage 3 and 4 respiration rates in mitochondrial preparations. 10. These observations imply that coenzyme A availability may have regulated de novo lipogenesis in the present study. 11. It was also concluded that previously noted effects of T3 on intermediary metabolism may involve metabolic pathways that do not involve changes in mitochondrial function.

Acetates↗

PubMed1993

Protein and energy relationships in the broiler chicken. Effects of protein quantity and quality on metabolism.

Male broiler chickens growing from 7 to 35 d were fed on a diet containing 150 g crude protein (N x 6.25)/kg diet supplemented with lysine to equal that in diets containing 166, 183 and 200 g crude protein/kg diet (Expt 1). A second group of male broiler chickens growing over the same period were fed on a diet containing 120 g crude protein/kg supplemented with lysine, arginine, tryptophan, threonine and isoleucine equal to that in diets containing 144, 172 and 200 g crude protein/kg diet (Expt 2). Growth was improved by lysine supplementation but not to the level attained by feeding 200 g crude protein/kg (Expt 1). Lysine, arginine, tryptophan, threonine and isoleucine supplementation of a low-protein diet also improved growth, but growth again fell short of that attained by feeding a diet containing 200 g crude protein/kg. Plasma insulin-like growth factor-1 and thyroxine concentrations increased and triiodothyronine decreased as the crude protein level increased from 150 to 200 g/kg diet. Supplemental lysine did not affect plasma levels of these hormones. Although dietary crude protein levels noticeably changed rates of in vitro lipogenesis, changing either the level of a single limiting amino acid or the levels of several limiting amino acids did not change lipogenesis.

Amino Acids↗

PubMed1993

Acute effects of administration of porcine growth hormone on circulating levels of hormones and metabolites in 20-, 40-, and 60-kilogram gilts.

Three groups of eight gilts weighing 20, 40, or 60 kg were fitted with indwelling venous catheters to determine daily integrated circulating levels (DICL, serum concentration above baseline x time) of insulin, growth hormone (GH), glucagon, glucose, urea, and nonesterified fatty acids (NEFA) in response to acute challenge with porcine pituitary GH (pGH). Pigs were fed a common diet containing 18% CP and 3.5 Mcal of DE/kg between 0800 and 1200 (85% of ad libitum). Blood and urine were collected at 2- or 4-h intervals for 4 d. On d 2, 3, and 4, four pigs in each group were injected i.m. at 0800 with pGH (.1 mg/kg) and four pigs (controls) were injected with buffer. In control pigs DICL of GH was 20.4, 14.1, and 10.2 ng pGH.h.mL-1 in 20-, 40-, and 60-kg pigs, respectively. The DICL of GH in pGH-treated pigs was 4.2-, 7.0-, and 10.7-fold greater in 20-, 40-, and 60-kg pigs, respectively, than in controls. The DICL of insulin in control pigs was 7.9, 9.7, and 9.4 ng.h.mL-1 and was increased (P < .001) in pGH-treated pigs by 118, 213, and 276% in 20-, 40-, and 60-kg pigs, respectively. Although serum levels of glucose were increased (P < .001) by pGH treatment, the acute elevation observed in 60-kg pigs was more consistent relative to 20- and 40-kg pigs. In contrast, the acute reduction in blood urea upon pGH injection was more apparent in 20-kg gilts.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Energy repletion and lipid metabolism during compensatory gain in broiler chickens.

Ross male broiler chickens were used to determine the effect of dietary energy on metabolism following a 6-day dietary energy restriction. Chickens were fed an amount of food (10 g) from 6 to 12 days of age calculated to only maintain body weight (maintenance energy) and not support appreciable growth. The chickens were then fed 1, 2, or 4x this amount of food for the period from from 13 to 21 days of age. Another group of chickens were also restricted from 6 to 12 days of age, but on an ad libitum basis from days 12 to 21. A control group was fed ad libitum throughout the experiment. All chickens were fed ad libitum from 21 to 54 days of age. Chickens were sacrificed at 12, 15, 17, 19, 22, 28, and 54 days. In vitro lipogenesis (IVL) and enzyme activities (isocitrate dehydrogenase; ICD, malic enzyme; ME, and glutamic oxaloacetic aminotransferase (GOT) were determined during the 12 to 28-day period and at 54 days. All restriction groups were lighter (P < 0.05) than controls at 28 days. Only chickens given 1x and 2x maintenance energy from 12 to 21 days were lighter (P < 0.05) than controls at 54 days. The 6-day energy restriction decreased (P < 0.05) IVL and ME and refeeding 2x and 4x maintenance restored IVL as did refeeding ad libitum. The greatest response was noted between 2 and 4 days following refeeding, surpassing controls at both periods. The significance of the present study lies in the findings that lipogenesis can be dosed against the energy intake following restriction and that changes in lipogenesis are very rapid, reaching steady state within 2 to 3 days. Furthermore, the growth data suggest that restriction regimens shift normal growth curves and compensatory growth may be an artifact of expressing data because smaller, younger birds have less fat than older birds.

Animal Feed↗

PubMed1992

In vitro lipid metabolism, growth and metabolic hormone concentrations in hyperthyroid chickens.

Indian River male broiler chickens growing from 7 to 28 d of age were fed on diets containing energy:protein values varying from 43 to 106 MJ/kg protein and containing 0 or 1 mg triiodothyronine (T3)/kg diet to study effects on growth, metabolic hormone concentrations and in vitro lipogenesis. In vitro lipid synthesis was determined in liver explants in the presence and absence of ouabain (Na+, K(+)-transporting ATPase (EC 3.6.1.37) inhibitor) to estimate the role of enzyme activity in explants synthesizing lipid. Growth and feed consumption increased (P < 0.01) when the energy:protein value decreased from 106 to 71 MJ/kg protein; however, both variables decreased as the value was further decreased from 53 to 43 MJ/kg protein. Triiodothyronine depressed (P < 0.01) growth, but not food intake. Large energy:protein diets (> 53 MJ/kg protein) and dietary T3 lowered (P < 0.01) plasma growth hormone. Large energy:protein diets (> 53 MJ/kg protein) increased (P < 0.01) lipogenesis, plasma growth hormone (GH) and decreased plasma insulin-like growth factor 1 (IGF-1). Also, T3 decreased plasma GH, IGF-1 in vitro lipogenesis. Ouabain inhibited a greater proportion of in vitro lipogenesis in those explants synthesizing fat at a high rate. Both dietary T3 and in vitro ouabain decrease lipogenesis, but, when combined, the effects are not cumulative.

Animals↗

PubMed1991

Effect of pulsatile or continuous administration of pituitary-derived chicken growth hormone (p-cGH) on lipid metabolism in broiler pullets.

1. The effects of pulsatile and continuous intravenous administration of exogenous, pituitary-derived chicken growth hormone (p-cGH) on lipid metabolism and endocrine/metabolite levels of broiler-strain pullets were studied. 2. Eight-week-old pullets were administered p-cGH or vehicle over a 10 min period every 90 min for 7 days. 3. Pullets were also administered the same daily amount (123 micrograms/kg of body weight/day) continuously for 7 days. 4. Feed intake, body weight gain, in vitro lipogenesis and hepatic enzyme activities were determined with certain hormones identified with the control of growth. 5. Pulsatile p-cGH administration for 7 days lacked effect on weight gain, feed efficiency, muscle or bone development. 6. Abdominal fat pad size was decreased (P less than 0.05) by pulsatile but not continuous administration of p-cGH. Pulsatile p-cGH administration also decreased (P less than 0.05) in vitro lipogenesis. Liver malic enzyme and isocitrate dehydrogenase activities were increased (P less than 0.05) by pulsatile but not continuous administration of p-cGH. In contrast, glutamic oxaloacetic transaminase activity was increased by a continuous infusion of p-cGH. 7. Plasma concentrations of T4 corticosterone and triglycerides were decreased (P less than 0.05) by a pulsatile but not a constant infusion of p-cGH. 8. Plasma T3 and GH were increased (P less than 0.05) by pulsatile p-cGH compared to both a continuous infusion of p-cGH and the saline controls. 9. This study is the first to prove that in the broiler chicken, the pattern of exogenous p-cGH administration is a factor influencing in vitro responses to the hormone.

Adipose Tissue↗