Effects of growth hormone treatment on the pituitary expression of GHRH receptor mRNA in uremic rats.
BACKGROUND
A decreased ability of pituitary cells to secrete growth hormone (GH) in response to growth hormone releasing hormone (GHRH) stimulation has been shown in young uremic rats. The aim of the current study was to examine the effect of uremia and GH treatment on pituitary GHRH receptor expression.


METHODS
Pituitary GHRH receptor mRNA levels were analyzed by RNase protection assay in young female rats made uremic by subtotal nephrectomy, either untreated (UREM) or treated with 10 IU/kg/day of GH (UREM-GH), and normal renal function animals fed ad libitum (SAL) or pair-fed with the UREM group (SPF). Rats were sacrificed 14 days after the second stage nephrectomy.


RESULTS
Renal failure was confirmed by concentrations (X +/- SEM) of serum urea nitrogen (mmol/L) and creatinine (micromol/L) in UREM (20 +/- 1 and 89.4 +/- 4.5) and UREM-GH (16 +/- 1 and 91.4 +/- 6.9) that were much higher (P < 0.001) than those of sham animals (SAL, 3 +/- 0 and 26.5 +/- 2.2; SPF, 4 +/- 0 and 26.5 +/- 2.1). UREM rats became growth retarded as shown by a daily longitudinal tibia growth rate below (P < 0.05) that observed in SAL animals (156 +/- 3 vs. 220 +/- 5 microm/day). GH treatment resulted in significant growth rate acceleration (213 +/- 6 microm/day). GHRH receptor mRNA levels were no different among the SAL (0.43 +/- 0.03), SPF (0.43 +/- 0.08) and UREM (0.44 +/- 0.04) groups, whereas UREM-GH rats had significantly higher values (0.72 +/- 0.07).


CONCLUSIONS
The status of pituitary GHRH receptor is not modified by nutritional deficit or by severe uremia causing growth retardation. By contrast, the growth promoting effect of GH administration is associated with stimulated GHRH receptor gene expression.
Ferrando
Susana
S
School of Medicine, Hospital Central de Asturias, University of Oviedo, C/Julián Clavería 6, 33006 Oviedo, Asturias, Spain.
Rodríguez
Julián
J
Santos
Fernando
F
Weruaga
Ana
A
Fernández
Marta
M
Carbajo
Eduardo
E
García
Enrique
E
D000818:Animals; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D013006:Growth Hormone / Q000494:pharmacology*; D007668:Kidney / Q000254:growth & development / Q000502:physiology / Q000601:surgery; D009392:Nephrectomy; D010902:Pituitary Gland / Q000254:growth & development / Q000502:physiology*; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D018013:Receptors, Neuropeptide / Q000235:genetics*; D018017:Receptors, Pituitary Hormone-Regulating Hormone / Q000235:genetics*; D014511:Uremia / Q000503:physiopathology*
D012333:RNA, Messenger; D018013:Receptors, Neuropeptide; D018017:Receptors, Pituitary Hormone-Regulating Hormone; D013006:Growth Hormone; C048250:somatotropin releasing hormone receptor