Influence of parasitism on plasma concentrations of growth hormone, somatomedin-C and somatomedin-binding proteins in calves

Abstract

A parasitic disease model (sarcocystosis) was used to study the effects of infection and associated plane of nutrition on GH and somatomedin-C (SM-C) patterns in plasma, and SM-C binding protein patterns in plasma from 4-month-old male Holstein calves. Calves, matched by age and rate of growth before the experiment, were divided into three treatment groups (n = 7). In the first (control), animals were uninfected and food was available ad libitum; in the second, animals were infected with Sarcocystis cruzi and food was available ad libitum. The third group consisted of uninfected animals pair-fed to the level of feed intake of the infected animals. Blood samples were obtained at various times after infection for analysis of the secretory patterns of GH (day 27 after infection, samples every 10 min for 6 h), SM-C (days 27, 35 and 58 after infection) or binding protein (day 42 after infection). Samples were analysed for GH and SM-C by radioimmunoassay. Relative molecular weights of binding proteins were assessed by elution patterns from gel permeation columns. Clinical signs of infection were manifest abruptly on day 26 after infection. Voluntary feed intakes of infected calves as a per cent of control calves were 18, 46 and 78 on days 27, 35 and 58 after infection respectively. Plasma GH concentrations were lower in infected and pair-fed than in control calves (P less than 0.05). Plasma SM-C concentrations were reduced in calves with diminished feed intakes and lower still in infected calves (P less than 0.05). Plasma SM-C was positively correlated with nitrogen retention across treatment groups (r = 0.81). Two classes of binding proteins differing in molecular weight were identified. The relative amounts of each binding protein in plasma were reduced during low feed intake with some differences in the endogenous saturation affected by infection. These data suggest that altered growth and metabolism in parasitized calves may arise in part from both nutritional and infection-mediated effects on the regulation of GH, SM-C and SM-C binding proteins.

Insulin-Like Growth Factor-I as a Possible Hormonal Mediator of Nutritional Regulation of Reproduction in Cattle

“…Increases in IGFBP-1 and -2 seem to restrict IGF-I activities, while a decrease in IGFBP-3 suggests an attempt to maximize the availability of remaining IGFs to the tissues. Elsasser et al [31] demonstrated reduced binding of IGF-I in calves due to restriction of intake and parasitism.…”

Protein tyrosine nitration in chronic intramuscular parasitism: immunohistochemical evaluation of relationships between nitration, and fiber type-specific responses to infection

“…Furthermore, it was demonstrated in our previous study that the observed muscle effects exceeded any of the effects associated with the temporary slump in voluntary feed intake where direct nutritional effects of nutritional plane were addressed statistically through the use of the applied pair-feeding strategy. 7 Protein tyrosine nitration is a posttranslational chemical modification wherein the 3'-position of the affected tyrosine phenolic structure becomes nitrated. 42 Though thought of principally as a biomarker for oxynitrogen stress and disease, 43 we now know that nitration in low, well controlled biological circumstances such as the selective nitration of JAK2 kinase by growth hormone 27 functions as a process important to signal transduction events, possible countering hormone and cytokine pathway processes activated by phosphorylation while the high levels of production indicate pathology.…”

“…4 Growth deficits and associated cachectic and atrophic metabolic responses (anorexia, fever production, protein and fat mobilization, liver acute phase protein synthesis) to infection in the young are evident not only in changes in body weight gain or height velocity over time but also observable as changes in body composition. 5 Using models of parasitemediated progressive inflammatory disease in calves, [6][7][8] we characterized organ and tissue depot-specific changes in chemical body composition associated with reduced rate of weight gain and/or weight loss during parasitic infection. In particular, we observed that the pattern of change in fat and protein content of impacted tissues was not uniform as regards the extent to which different tissue depots were affected.…”

Administration of bovine anti-IGF-1 immunoglobulin to dietary protein deficient rats alters dietary intake and plasma IGF-1 binding profiles, but does not affect change in body mass

“…In cattle, retained nitrogen (Elsasser et al, 1988) and body weight (BW) gain (Breier et al, 1988) have been correlated with circulating IGF-1 during feed restriction. Ogawa et al (1996) observed a negative correlation between net protein catabolism and plasma IGF-1 levels during GH treatment of fasting lambs.…”