Molecular heterogeneity of circulating prolactin in chronic uremic men and renal transplant recipients.

Serum PRL levels and its molecular heterogeneity were analyzed, basally and after 500 micrograms TRH given acutely, in four groups of men: normal (C, n = 12), chronic renal failure (CRF, n = 11), hemodialysis (HD, n = 12), and transplant recipients (T, n = 11). The mean basal PRL level was higher in group CRF than in group C and even higher in group HD. The basal hyperprolactinemia was due to increased concentrations of little PRL. The absolute levels of total and little PRL 20 min after TRH were comparable in the four groups. The disappearance index (DI = PRL20-PRL120/PRL20) for total and little PRL was lower in CRF than in C and even lower in HD. A positive correlation was found between the DIs of total and little PRL and creatinine clearance in group CRF. Group T had basal and 20 min serum PRL levels and a pattern of molecular distribution similar to those of group C but total and little PRL DI was lower. These results demonstrate that uremic hyperprolactinemia is due to increases in little PRL without major changes in big and big-big forms of PRL. The reduction of glomerular filtration rate seems to be one of the most important mechanisms responsible for little PRL accumulation.

Prolactin plasma levels and its size heterogeneity in acutely uremic rats.

The size distribution pattern of circulating rPRL was studied in intact control (C) rats and in three uremic models, namely urine autoinfusion (UA), bilateral ureteral ligation (BUL), and bilateral nephrectomy (BNx). Plasmas were chromatographed by gel filtration in Sephadex G-100. Rat PRL was measured by RIA. The rPRL levels as well as the size distribution pattern of UA were similar to that of C. BUL and BNx showed a similar degree of hyperprolactinemia which corresponded to an increase in little rPRL. The results suggest that acute uremic hyperprolactinemia seems to be the result of accumulation of little rPRL. Acute uremia by itself does not increase rPRL plasma levels nor does it seem to affect the size distribution pattern of circulating rPRL.

Functional compensatory changes after unilateral nephrectomy in rats. General and intrarenal hemodynamic alterations.

Cardiac output (CO), total peripheral resistance (TPR), renal blood flow (RBF), renal vascular resistance (RVR) and intrarenal blood flow distribution have been measured 48 h after unilateral (right) nephrectomy (UNX) and in sham-operated rats (SO). Glomerular filtration rate (GFR) and renal plasma flow (RPF) were determined using standard inulin and PAH clearances. Superficial single nephron GFR (SNGFR) was measured by free-flow micropuncture techniques. Extracellular fluid volume (ECV) and plasma volume (PV) were also determined. UNX rats showed increases of 17.4% in remnant kidney GFR and 34.5% in RPF. Filtration fraction was decreased to 0.27 +/- 0.01 (control value 0.31 +/- 0.01; p less than 0.0025). SNGFR was 45% higher in UNX rats and the ratio SNGFR/GFR increased by 28%. Cardiac output also increased (33.6 +/- 1.0 for UNX rats; 28.0 +/- 1.2 ml/min/100 g BW for SO rats; p less than 0.0025) accompanied by a corresponding fall (20%) in TPR. Left kidney RBF increased by 22%, whereas RVR decreased by 21%. Blood flow through individual glomeruli increased in the outer and inner cortex and was unchanged in the midcortex. In conclusion, 48 h after unilateral nephrectomy, rats showed a hyperdynamic circulatory state with increased CO and decreased TPR; this could be involved in the acute adaptive functional and renal changes reported after uninephrectomy.

Pathogenesis of hyperprolactinemia in uremic rats.

Experiments have been carried out in order to clarify to what extent the absence of PRL renal catabolism in experimental renal insufficiency is responsible for the high PRL circulating levels. Furthermore, the relative contribution of the glomerular filtration rate and peritubular degradation to PRL renal clearance have been assessed. Circulating PRL basal levels were measured by RIA in sham-operated and intact control rats and in three uremic rat models: urine autoinfusion, bilateral ureteral ligation, and bilateral nephrectomy. Plasma PRL basal levels (nanograms per ml; mean +/- SEM) were increased in sham-operated rats (30.3 +/- 5.1) with respect to control animals (18.5 +/- 2.7; P less than 0.05). Bilaterally nephrectomized animals (66.4 +/- 16.4) and those with bilateral ureteral ligation (69.3 +/- 15.9) developed similar hyperprolactinemia, in contrast to urine-autoinfused rats (20.2 +/- 2.1; P less than 0.005) whose hormone levels were similar to those of control animals. Creatinine levels were markedly elevated and comparable in the three uremic rat groups. The results suggest that: 1) hyperprolactinemia in rats in acute renal insufficiency is due primarily to reduced renal function; 2) PRL renal catabolism in the rat requires a certain rate of glomerular filtration; and 3) PRL peritubular degradation does not seem to be relevant in PRL catabolism by rat kidney.

[Measurement of the cardiac output and its peripheral distribution in rats by means of radioactive microspheres (author's transl)]. / Medida del gasto cardíaco y su distribución periférica en ratas utilizando microesferas radiactivas.

The cardiac output (CO), the blood flow (BF) through several organs and the peripheric resistances have been simultaneously determined on uninephrectomized rats by using two kinds of microsphere with a theoretical diameter of 15 micrometer and labeled with 141Ce or 85Sr. The measured diameter of the microspheres was 13.1 +/- 0.2 micrometer (n = 500) for the 141Ce labeled microspheres and 16.2 +/- 0.3 micrometer (n = 500) for the 85Sr ones. The difference is statistically significant (p < 0.005). Both kinds of microspheres gave comparable values for the CO and the renal, splenic and heart coronary; BF, but quite dissimilar for the hepatic and pulmonary BF. the resulting CO (29.0 +/- 2.4 ml/min-1/100 g-1) is very similar to those reported in the literature and likewise with the splenic, coronary and renal BF, correlating the latter closely with the value obtained from the PAH clearance. In conclusion, the microspheres technique seems to be a simple and timesaving method to measure the CO and BF of such organs as kidneys, spleen and heart of the rat.