Increased IGF-I Concentrations Research Articles

Lactation performance of sows fed a bulky diet during gestation and receiving growth hormone-releasing factor during lactation.

Forty-eight crossbred gilts were used in an experiment with a 2 x 2 x 2 factorial arrangement of treatments. Treatments were control or bulky diet during gestation (4.1 vs 15.3% crude fiber), number of meals served daily in lactation (2 vs 4), and three daily s.c. injections of saline or of 1 mg of a human growth hormone-releasing factor analog (GRF-AN) from d 3 to 29 of lactation. Weights of pigs were recorded weekly until weaning on d 33. On d 29 of lactation, milk yield was estimated and a milk sample was obtained the next day. Jugular blood samples were collected from the sows on d 3 and 28 of lactation. Feed and water intake of sows were recorded throughout the study. Feeding the bulky diet decreased water intake in gestation (P < .001) and increased feed intake in lactation (P < .03). The number of meals served daily had no effect on feed intake during lactation (P > .1). Injections of GRF-AN increased IGF-I concentrations in blood (P < .01) and in milk (P < .001) and decreased backfat thickness (P < .001) and feed intake (P < .001) of sows during lactation. Pigs from sows injected with GRF-AN weighed more on d 14 (P < .05) and had a tendency to weigh more on d 7 (P = .09) and d 21 (P = .06). The incidence of sows showing estrus within 10 d of weaning was reduced with exogenous GRF (P < .01). The use of exogenous GRF in lactating sows may therefore have beneficial effects on growth of the pigs, yet the optimal nutritional and hormonal conditions needed for GRF to exert its full potential still need to be determined.

The Effect of Feed Intake and Growth Hormone-Releasing Factor on Lactating Dairy Cows

Twenty-four lactating dairy cows, averaging 30.0kg/d of milk and 159 d of lactation, were used to study the effect of feed intake and growth hormone-releasing factor in a 2×2 factorial arrangement. For the first 10-d period, cows had free access to a TMR and received a fixed amount of high moisture corn, protein supplement, and hay. In the second 10-d period, 12 cows were maintained on this high intake, and 12 cows received 70% of their previous intake (low intake). During the following 10-d period, each intake group was divided, and each of two subgroups (n=6) received twice daily s.c. injections of saline or growth hormone-releasing factor (10μg/kg of BW per injection). Feed restriction decreased milk production by 24%. Milk production increase was not different following growth hormone-releasing factor treatment for cows maintained at high intake (4.6kg/d) or low intake (3.4kg/d). Feed restriction increased concentration of growth hormone but did not affect IGF-I concentration. Growth hormone-releasing factor increased IGF-I concentration similarly for both intake groups but increased concentrations of insulin and IGF-binding proteins-1 and -3 only in the high intake group. Low intake did not affect growth hormone, IGF-I, or milk responses to growth hormone-releasing factor, but suppressed the increase in concentrations of insulin and IGF-binding proteins-1 and -3 following treatment with growth hormone-releasing factor for cows on high intake.

Endocrine Evaluation in Patients Treated with Interferon-Alpha for Chronic Hepatitis C

The aim of our study was to evaluate the hormonal profile in a group of 31 subjects who underwent recombinant interferon-alpha therapy for chronic active hepatitis C. Hormonal determinations were performed before treatment began and at the end of the 3rd and 6th months of therapy. Free-T4 concentrations, though remaining in the normal range, showed a significant reduction (p < 0.05) after 3 and 6 months of therapy compared with pretreatment levels. A lesser decrease in free-T3 levels was also seen. TSH basal values did not show any variation, while an increased secretory response to TRH stimulation was observed at the end of the 6th month. Thyroglobulin and calcitonin levels remained normal, while an increase in antithyroglobulin and antithyreoperoxidase antibody levels was observed in 4 patients (12.9%). No modifications in the other pituitary hormones or in adrenal and sex steroid concentrations were noticed. A significant increase in IGF-I concentrations (p < 0.05) was observed during treatment, and an inverse correlation was seen between IGF-I and alanine aminotransferase levels (p < 0.01). This study supports the view that interferon treatment can influence thyroid function. The increase in IGF-I concentration observed during therapy may reflect an improvement in patients with hepatic disease, but a direct stimulatory effect of interferon on IGF-I secretion cannot be excluded.

Porcine somatotropin (pST) increases IGF-I mRNA abundance in liver and subcutaneous adipose tissue but not in skeletal muscle of growing pigs

The present study was undertaken to determine the effects of exogenous porcine somatotropin (pST) on IGF-I gene expression in liver, skeletal muscle (longissimus dorsi), and s.c. adipose tissue of growing pigs. Twenty prepubertal gilts (approximately 60 kg BW) were allotted to four treatment groups (n = 5) and treated with either 0, 35, 70, or 140 micrograms/kg BW of recombinantly derived pST by daily i.m. injection for 7 d. Serum concentrations of IGF-I were determined by RIA and IGF-I mRNA levels were determined by direct counting of individual samples on slot blots. Administration of pST increased IGF-I concentration in serum. This was accompanied by significant increases (P < .05) in IGF-I mRNA abundance in liver and s.c. adipose tissue; the effects were maximal at the lowest dose of pST. Insulin-like growth factor I mRNA levels were increased 2.5- and 4.5-fold, respectively. Levels of IGF-I mRNA were very low in longissimus muscle and were unaffected by administration of pST. When expressed as picograms of mRNA/10 micrograms of total RNA, IGF-I mRNA levels were highest in s.c. adipose tissue. Levels of IGF-I mRNA were 1.9-fold higher in s.c. adipose tissue than in liver of control animals, and pST administration increased this difference to 3.2-fold. Our results suggest that 1) the effects of pST administered by daily i.m. injection on IGF-I gene expression in pigs are tissue-specific and 2) the stimulatory effects of pST administered in this manner on muscle growth in pigs are not associated with increased expression of the IGF-I gene in skeletal muscle.

Growth and hormonal response of intact and castrate male cattle to trenbolone acetate and estradiol.

Effects of castration and anabolic implants on weight gain, rib soft tissue composition and serum hormones were studied in cattle using a completely random design with a 2 x 2 factorial arrangement. Half of 16 bulls and 16 steers (Angus or Angus x Brahman) aged 9 mo and weighing 290 kg were treated with an implant (200 mg trenbolone acetate and 24 mg estradiol). Half of each group were not treated with an implant. A growing diet was fed for 95 d and half the animals in each group were slaughtered. Animals in the treated groups were reimplanted with trenbolone acetate and fed a finishing diet for 84 d and slaughtered. Percentage dry matter, fat and protein were determined on soft tissue from the 9-10-11th rib. Two blood samples were collected from each animal every 2 wk. Serum was assayed for five hormones. During the growing phase, untreated and treated bulls and treated steers gained more weight and had leaner rib sections that untreated steers (P less than .05); after the finishing phase, there were no differences among groups. Untreated steers had lower insulin-like growth factor (IGF-I) and higher cortisol concentrations during both phases of growth than untreated bulls did (P less than .05). Treatment with implants increased IGF-I concentrations in steers during both phases and reduced cortisol during the finishing phase.(ABSTRACT TRUNCATED AT 250 WORDS)