Growth hormone secretory capacity of individual somatotropes in rats with chronic renal insufficiency

Growth failure is a common consequence of chronic renal insufficiency (CRI) in children and may be due to a number of factors. With regard to growth hormone (GH), regulation is often abnormal in CRI patients. The present study investigated the effect of CRI on the GH secretory responsiveness to GH-releasing hormone in individual rat pituitary somatotropes. Male Sprague-Dawley rats underwent a 5/6 nephrectomy to produce CRI. Control rats (SHAM) received sham operations, which included kidney decapsulation but not removal. Two wk later, during a period of stable uremia, serum creatinine [CRI: 1.1 +/- 0.08 mg/dL (97 +/- 7 mumol/L); SHAM: 0.4 +/- 0.04 mg/dL (35 +/- 4 mumol/L)] and serum urea nitrogen [CRI: 60.7 +/- 8.3 mg/dL (21.7 +/- 3.0 mmol/L); SHAM: 15.8 +/- 1.2 mg/dL (5.6 +/- 0.4 mmol/L)] were significantly elevated in the CRI rats (p less than 0.0005). Weight gain (p less than 0.0005), length gain (p less than 0.0005), food intake (p less than 0.0005), and food efficiency (p less than 0.005) were all significantly lower in the CRI rats. The GH secretory capacity of individual somatotropes was determined using the reverse hemolytic plaque assay technique. Plaque areas were measured to assess relative amounts of GH secreted. The total number of pituitary cells per rat, the percentage of somatotropes, and the mean plaque areas were similar for the two groups. These findings compare favorably with our in vitro study of GH responsiveness in perifused rat pituitary cells under conditions of mild uremia.