Porcine calcitonin as a renal vasodilator in man

Vasodilator Effects of Elcatonin, a Synthetic Eel Calcitonin, on Retinal Blood Vessels in Rats

The aim of this study was to examine the effects of elcatonin, a synthetic derivative of eel calcitonin, on rat retinal blood vessels, and to determine how diabetes affects the retinal vascular responses. Ocular fundus images were captured with an original high-resolution digital fundus camera in vivo. The retinal vascular responses were evaluated by measuring the diameter of retinal blood vessels contained in the digital images. Both systemic blood pressure and heart rate were continuously recorded. Elcatonin increased the diameter of retinal blood vessels but decreased mean blood pressure in a dose-dependent manner, whereas it had no significant effect on heart rate. A diminished retinal vasodilator response and significant pressor response to elcatonin were observed in rats injected intravenously with N(G)-nitro-L-arginine methyl ester, a nitric oxide (NO) synthase inhibitor. Intravitreal injection of indomethacin, a non-selective cyclooxygenase (COX) inhibitor, and SQ22536, an adenylyl cyclase inhibitor, markedly attenuated the vasodilator effects of elcatonin on retinal blood vessels. The retinal vasodilator responses to elcatonin were unaffected 2 weeks after the induction of diabetes by a combination of streptozotocin treatment and D-glucose feeding. These results suggest that elcatonin dilates rat retinal blood vessels via NO- and COX-dependent mechanisms and that the adenylyl cyclase-adenosine 3',5'-cyclic monophosphate system plays a major role in the vasodilator mechanisms. The retinal vasodilatory effects of elcatonin seem to be preserved at early stages of diabetes.

Chronic calcitonin administration and renal calcium transport in the rat

1. While calcitonin (CT) has now been clearly demonstrated to be a renal Ca2+-conserving hormone and may share similar transport mechanisms with parathyroid hormone (PTH), the effect of prolonged CT exposure on renal Ca2+ transport has not been evaluated. 2. Consequently, a submaximal and maximal Ca2+-conserving concentration of human CT was infused into groups of anaesthetized acutely thyroparathyroidectomized rats that had been treated with twice daily subcutaneous human (h) CT at a low or high dose or vehicle for 12 days. 3. The maximal hCT infusion (10 microg bolus and per hour) produced a marked inhibitory effect on renal Ca2+ excretion in vehicle-treated rats, with the fractional excretion rate of Ca2+ being reduced from 4.49+/-0.31 to 139+/-0.23% (P<0.001). However, in rats pretreated with high concentrations of hormone (0.25 microg hCT) twice daily for 12 days, marked Ca2+ conservation was measured (fractional excretion 1.09+/-0.18%), which was not altered by the additional intravenous administration of maximal hCT. 4. Renal Mg2+ transport was similarly altered by hCT administration, without any evidence that prolonged CT inhibited renal Mg2+ transport. The increase in glomerular filtration rate caused by hCT also appeared to persist with repeated hormone administration. The fractional excretion of Na+ and PO4 was significantly increased by high- but not low-dose hCT treatment and was not altered by the addition of a maximal hormone dose at day 12. 5. The present study failed to demonstrate any down-regulation of the response to prolonged hCT administration when renal Ca2+ and Mg2+ transport was measured. If renal escape does occur with CT, as has been suggested but not proven with PTH, other mechanisms, such as hormone production or release, may be responsible.

Technetium-99m autologous phagocyte scanning: a new imaging technique for inflammatory bowel disease

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Urinary sodium and calcium in various dog models and relationship to endogenous plasma glucagon

Clearance studies were performed in 23 dogs undergoing extracellular volume (ECV) expansion by saline in order to evaluate relationship between endogenous glucagon and renal excretion of sodium and calcium. In control animals plasma glucagon (pG1) rose following 120 minutes of ECV expansion and was further increased by additional infusion of arginine. In pancreatectomised dogs ECV expansion failed to increase pG1. Both fractional and absolute urinary excretion of sodium in pancreatectomised dogs were markedly lower compared to control dogs. The difference in renal sodium excretion between control and pancreatectomised animals cannot be explained by the sum of nonhormonal factors influencing sodium excretion. In thyro-parathyroidectomised dogs renal sodium excretion was lower than in control dogs, but significantly higher than in pancreatectomised dogs. The arginine-induced increase of glucagon was associated with an increase of renal sodium and calcium excretion in each group under study without any change in glomerular filtration rate. In control dogs all parameters of renal sodium and calcium excretion investigated in this study were linearly correlated. Thyro-parathyroidectomy did not influence the relationship between renal sodium and calcium excretion. Hyperglucagonaemia therefore might be one factor contributing to the hypercalciuria associated with renal stone formation. In pancreatectomised dogs undergoing ECV expansion there was no significant correlation between renal sodium and calcium excretion. Pancreatic hormones might be involved in the coupling of renal sodium and calcium excretion.

Carcinoid syndrome: its relevance to the anaesthetist

This paper presents the pathology, pharmacophysiology and therapy of the carcinoid syndrome. Forty reports from the literature are reviewed and the anaesthetic management of the patients is discussed. The carcinoid syndrome is a rare multihumoral endocrine disease. Secretions may be stimulated by certain anaesthetic and surgical manoeuvres and produce undesirable, and occasionally fatal, cardiovascular and respiratory complications. A radical surgical approach to the disease is current. Anaesthetists may therefore be involved in the management of these patients more frequently than before. The implication of both serotonin and bradykinin in the pharmacophysiology of this disease allows a more rational approach to the treatment of complications occurring during anaesthesia. However, other, as yet undiscovered vasoactive substances, may be involved.