Steroid Hormone May Modulate Hepatic Somatomedin C Production in Newborn Calves

Abstract

We have studied the possible influence of steroid hormones and a β-agonist (clembuterol) on hepatic insulin-like growth factor 1 (IGF₁) production in young calves. For this purpose nine 20- to 40-day-old Holstein × Friesian male calves were fitted with chronically indwelling catheters in hepatic and portal veins and hepatic artery. Estradiol induced a simultaneous increase in plasma growth hormone (GH nmol/l) and IGF₁ (nmol/l) levels (0.35 ± 0.05 vs. 0.10 ± 0.01 in control calves; 9.5 ± 1.0 vs. 5.9 ± 0.5 in controls, respectively). In the same way, 90 min after starting testosterone treatment, plasma GH levels increased from 0.21 ± 0.08 to 1.30 ± 0.40 while plasma IGF₁ concentrations began to rise only 240 min after starting infusion (8.4 ± 1.0) to reach maximal values at 300 min (10.7 ± 1.1). Cortisol and clembuterol did not significantly modify either plasma GH levels or plasma IGF₁ concentrations. Our results indicate that in young calves gonadal steroids exert their anabolic action through GH and IGF₁.

Effects of dexamethasone and colostrum intake on the somatotropic axis in neonatal calves

“…Because glucocorticoids are important for neonatal maturation (7), reduced GH concentrations after Dexa treatment in our study might indicate enhanced maturation of the somatotropic axis, as shown in neonatal pigs (10). On the other hand, cortisol treatment in 1-mo-old calves did not affect plasma GH concentrations (15). Because glucocorticoids have stimulatory and inhibitory effects on pituitary GH production and release (38), effects of glucocorticoids on GH secretion may depend on the developmental status.…”

“…However, our data correspond to findings in neonatal pigs (10) and growing bulls (43) treated with Dexa. However, Coxam et al (15) did not find an effect of cortisol on plasma IGF-I concentrations in calves, and Dexa decreased plasma IGF-I concentrations in cows and finishing calves (2,33). Therefore, effects of glucocorticoids on IGF-I plasma concentrations are variable and may depend on treatment-dose (34) and age (9).…”

Nutritional physiology of neonatal calves*

“…Furthermore, neonatal calves are able to produce IGF‐1 since IGF‐1 mRNA is expressed in liver, GIT, spleen, thymus, lymph nodes and kidney (Cordano et al., 2000; Pfaffl et al., 2002; Ontsouka et al., 2004a–c). Administration of bovine GH increases plasma IGF‐1 concentrations (Coxam et al., 1988; Grütter and Blum, 1991b; Hammon and Blum, 1997b) and there are significant changes of IGF binding proteins 1–3 in response to differences in feeding and endocrine treatments (Hammon and Blum, 1997b; Sauter et al., 2003). Although the GH‐IGF‐1 axis in neonatal calves is basically functional, the system is not fully mature because hepatic IGF‐1 expression in neonatal calves is small (Cordano et al., 2000; Pfaffl et al., 2002), and GH effects on the IGF systems are markedly smaller in neonatal calves than in older cattle.…”

Intestinal Development in Neonatal Calves: Effects of Glucocorticoids and Dependence on Colostrum Feeding¹

“…From day 3 onwards, the calves were fed daily at 08.00 and at 16.00 h. Additionally, the GrFD + and GrCD + calves were injected intramuscularly with DEXA (30 Ìg/kg/day, DEXA TAD; Lohmann Animal Health, Cuxhaven, Germany) twice daily at feeding times from day 1 to day 4. The dose of DEXA was chosen based on previous studies in animals [3,18]. D-Xylose (0.5 g/kg) was added to the morning meal of all calves on day 3 to study the intestinal xylose absorption capacity.…”

“…In each feeding group, half of the calves were treated by DEXA (GrCD + and GrFD + ). a The calves were treated twice daily at feeding times; the dose of DEXA was chosen according to previous studies in neonatal calves [18]. b Colostrum and formula were fed in amounts of 6% of body weight.…”