Reconciliation between urea kinetics and direct dialysis quantification.

Previous studies comparing urea kinetic model (UKM) and direct dialysate quantification technique (DDQ) found statistically different results as far as the urea distribution volume (V) and protein catabolic rate (PCR) are concerned. In these studies, however, the true values for both the dialyser urea clearance (K) and urea concentration (C) were not used. The aim of this study was to compare UKM and DDQ using for both methods a variable-volume single-pool (VVSP) model as well as plasma water C and effective K. The study was performed during paired filtration dialysis (PFD) sessions because this technique allows bloodless measuring of K. Twenty dialysis patients were studied during a single PFD session. Dialysate and ultrafiltrate C and urea mass transfer rate were measured every 15 min to compute averaged K and total urea removal. Blood samples were obtained as for a three-point UKM, and an iterative technique was used for both methods. The results (means +/- SD) obtained with UKM were as follows: K = 176 +/- 23 ml/min; V = 29986 +/- 7620 ml, PCR = 65 +/- 15 g/day, Kt/V = 1.04 +/- 0.17. These results were not statistically different from those obtained using DDQ. In conclusion, when methodological errors are avoided, DDQ and UKM provide very similar results. This study shows also that PFD is very useful for studying solute kinetics during dialysis.

Effect of the hormonal contraception on serum reverse triiodothyronine levels.

Thyroid hormones and the thyroxine-binding globulin are increased during hormonal treatment with oral contraceptives without changes in the thyroidal economy. Now we report that even reverse triiodothyronine, the main peripheral catabolite of thyroxine, is significantly increased during therapy with oral contraceptives.

Basal and forskolin-stimulated cyclic adenosine monophosphate in intact human platelets during the menstrual cycle.

In previous studies we observed modifications of cyclic adenosine monophosphate and adenylate cyclase activity in human endometrium during the menstrual cycle. In the present study our intension was to verify whether these modifications occur in isolated intact platelets. The results demonstrate that in nine normal women platelet cyclic adenosine monophosphate content varies during the menstrual cycle both in basal and in stimulated conditions (in vitro addition of forskolin). In fact, significantly higher levels of cyclic adenosine monophosphate were consistently observed during the proliferative phase. These findings provide evidence that platelet cyclic adenosine monophosphate metabolism normally varies during the menstrual cycle, which suggests a possible involvement of this system in some important clinical events.

Influence of acute estrogenic withdrawal on blood calcitonin.

As a model to investigate the pathogenesis of postmenopausal osteoporosis and the involvement of calcitonin in the bone alterations, we chose surgical menopause, studying the influence of castration on blood calcitonin. After surgery, the hormone and calcemia were raised significantly over preoperative values in castrated women, but not so in a control group of patients undergoing hysterectomy without oophorectomy. The elevated concentration of calcitonin was maintained during at least 4 months. It is speculated that this mechanism of control of calcitonin secretion by gonadal hormones might be activated in the pathogenesis of postmenopausal osteoporosis.