Growth hormone (GH) modulates insulin-like growth factor I (IGF-I) and type I IGF receptor mRNA levels in the ovary of prepubertal GH-deficient rats

Abstract

In order to explore the potential role of growth hormone (GH) in modulating insulin-like growth factor I (IGF-I) gene expression in the prepubertal rat ovary, female rats were rendered GH deficient by neonatal administration of monosodium glutamate (MSG). One group of rats received vehicle and served as the control. At 21 days of age, MSG-treated rats received either GH or vehicle for 2 weeks. On days 21, 24, 28 and 31 animals were weighed and subsets were sacrificed for liver RNA extraction. The remaining animals were sacrificed at day 35 when livers and ovaries were collected, and serum was obtained for GH determinations. The IGF-I mRNA levels were estimated by Northern blots and corroborated further by slot-blot analysis. The MSG-treated rats had lower body weights (p < 0.01) and GH levels (p < 0.05) than controls. Growth hormone replacement significantly accelerated the weight gain of MSG-treated rats. At day 24 and thereafter, three RNA IGF-I species (7.5, 1.8 and 0.8-1.2 kB) were seen in the liver. In the ovary, at age 35 days, two major IGF-I mRNA species (7.5 and 0.8-1.2 kb) were seen. The MSG treatment consistently reduced the levels of both IGF-I mRNA species in the ovary. Growth hormone administration partially restored their expression, both in the liver and in the ovary. In addition, ovarian type IIGF receptor mRNA levels were increased in the MSG-treated rats when compared to controls. This trend was reversed by GH replacement.(ABSTRACT TRUNCATED AT 250 WORDS)

Ovarian expression of insulin-like growth factor-I (IGF-I), IGF binding proteins, and growth hormone (GH) receptor in heifers actively immunized against GH-releasing factors

“…However, a recent study reported that ovarian levels of lGF-I mRNA were decreased in young rats made GH deficient by treatment with monoso dium glutamate. This effect was reversed by GH treatment (29). Similar to our findings, Samaras et al (30) reported that ovarian lGF-l mRNA levels were not altered in prepubertal gilts after 20 or 40 days of exogenous GH treatment in spite of increased levels of lGF-l in both serum and FFL.…”

A single growth hormone (GH) determination is sufficient for the diagnosis of GH‐deficiency in adult patients using the growth hormone releasing hormone plus growth hormone releasing peptide‐6 test

“…It is safe, with no side‐effects or contra‐indications, reproducible, unaffected by metabolic variables, such as free fatty acids, glucose, etc. (Dieguez & Casanueva, 1995; Maccario et al ., 1995; Malozowski et al ., 1995; Catalina et al ., 1998; De Marinis et al ., 2000), and explores the whole hypothalamus‐stalk‐pituitary axis (Pombo et al ., 1995; Popovic et al ., 1995). It is also unaffected by the GH levels at the begining of the test.…”

A somatotrofina bovina recombinante sobre a ovulação, condição corporal e níveis séricos de colesterol e glicose em ovinos

“…Em um sentido geral, a somatotrofina antagoniza a ação da insulina, porém, algumas vezes, sua ação é exercida de modo indireto via IGF-1, receptores e proteínas ligantes. Metabolicamente a somatotrofina é inibida pela hiperglicemia, por níveis crescentes de ácidos graxos e pela obesidade (NORMAN & LITWACK, 1987;MALOZOWSKI et al, 1995).…”