Role of the kidneys in elimination of glucagon, insulin, secretin and somatostatin in the rat

Somatostatin release in response to glucose is impaired in chronic renal failure

In order to evaluate somatostatin (SRIH) secretion in uremia, plasma SRIH concentrations were determined in basal conditions and after an oral glucose tolerance test (OGTT) in 14 non-dialysed patients with chronic renal failure (CRF), seven of whom had normal glucose tolerance (NGT) and seven impaired glucose tolerance (IGT). Plasma insulin, C-peptide and glucagon and blood glucose concentrations were also evaluated. The results were compared with those obtained in a group of age- and sex-matched normal subjects. In CRF patients, plasma SRIH fasting values (8.6 +/- 0.6 and 7.8 +/- 0.6 pmol/L in NGT and IGT patients, respectively) were comparable to those recorded in controls (7.7 +/- 0.5 pmol/L). SRIH response to OGTT, evaluated as area under curves (AUC) above basal, was similar in both groups of CRF patients (412.9 +/- 84.5 and 415.6 +/- 51.9 pmol/L per min), and significantly lower than in controls (660.1 +/- 58.5 pmol/L per min). Data indicate that chronic uremia induces a loss of SRIH secretory cell responsiveness to glucose. A possible effect of impaired SRIH secretion on glucose metabolism in CRF is discussed.

Distribution of i.v. administered epidermal growth factor in the rat

The distribution of i.v. injected 125I-labeled epidermal growth factor (EGF) was examined in the rat. The uptake of radioactivity was examined for the following tissues: liver, kidney, skin, stomach, small intestine, colon, brain, submandibular gland, lung, spleen, and testis. 125I-EGF was cleared from the circulation within minutes. At 2.5 min after the injection only 7% of the label was left in the blood. Most of the label was found in the liver (52%), the kidneys (14%), the small intestine (11%) and the skin (7%). The other organs examined contained 1% or less of the radioactivity. The uptake of 125I-EGF per g tissue was markedly higher for the liver and kidneys than for the rest of the organs. By autoradiography 125I-EGF was found in the peripheral parts of the classical liver lobule, in the proximal tubules of the kidneys, in the surface epithelium of the stomach, and in the surface epithelium of the villi in the small intestine. In conclusion the present study showed that small doses of homologous EGF was cleared from the circulation of rats within minutes, mainly by the liver, the kidneys, and the small intestine.

Influence of experimental acute renal failure on somatostatin levels and binding in rabbit fundic and duodenal mucosa

Rabbits with bilateral ureteral ligation of four-days duration showed a significant decrease of somatostatin content in gastric fundic mucosa (but not in proximal duodenal mucosa) as well as in the binding capacity of both high- and low-affinity binding sites without changes in the affinity values in cytosol of fundic and proximal duodenal mucosa, whereas the fasting plasma somatostatin levels increased as compared to control conditions. The number of somatostatin binding sites was inversely related to plasma levels of the peptide and support the hypothesis of somatostatin regulating its own binding sites. The current finding provides evidence that diminished somatostatin binding may be a contributory factor in the somatostatin gastroduodenal resistance of uremia.

The effect of nephrectomy and ureter ligation on plasma neurotensin-like immunoreactivity levels in the conscious rat

The effect of nephrectomy and ureter ligation on the concentration of endogenous plasma neurotensin-like immunoreactivity (p-NTLI) was studied in conscious rats by means of antiserum 17-8201 which detects NT (1-13) only, and antiserum 0-7709 which detects NT(1-13) and NT(1-8). The unstimulated p-NTLI concentration did not change significantly during a 25-h observation period following nephrectomy in comparison with sham operation. However, stimulation of the release of NTLI by intraduodenal administration of oleic acid (0.2 ml) resulted in significantly higher p-NTLI levels in the nephrectomized rats than in the sham operated rats. Ureter ligation did not significantly affect basal or stimulated p-NTLI. The data indicate that the kidneys play an important part in the elimination of p-NTLI released after fat ingestion.

Mechanism of gastric acid response to pylorus ligation: effects of nephrectomy

In the rat nephrectomy raises the serum gastrin concentration but makes the parietal cells refractory to gastrin. Pylorus ligation stimulates the gastric acid output by a long vago-vagal reflex in innervated animals and by an intramural reflex in chronically vagotomized animals. Nephrectomy reduced the acid response to pylorus ligation in vagally intact rats but enhanced it in vagotomized rats. The acid response to pylorus ligation in all the experimental groups was inhibited by a muscarinic blocker, atropine, and by an H2-antagonist, metiamide. The serum gastrin concentration was raised by nephrectomy and by vagal denervation. Histamine mobilization from gastric endocrine cells is reflected in the activity of gastric histidine decarboxylase. The enzyme activity in pylorus-ligated innervated rats was raised by pentagastrin, atropine, and metiamide. In nephrectomized rats the basal enzyme activity was high, and it was raised further, slightly but significantly, by pentagastrin. The basal enzyme activity in pylorus-ligated rats was also quite high after vagotomy, and it was raised further by pentagastrin. After vagotomy + nephrectomy the basal enzyme activity was very high; it was not raised further by pentagastrin. It appears that both vago-vagal and intramural reflexes involve a cholinergic and a histaminergic pathway, that gastrin is not important for the neurally mediated acid response elicited by pylorus ligation, and that the postulated histaminergic pathway does not involve histamine derived from the gastric endocrine-like cells.