Regulation of sodium, calcium and vitamin D metabolism in Dahl rats on a high-salt/low-potassium diet: genetic and neural influences.

1. A dietary combination of high salt and low potassium (HSLK) exacerbates hypertension in Dahl salt-sensitive (DS) rats and renders previously normotensive Dahl salt-resistant (DR) rats hypertensive. In both strains, the severity of hypertension correlates with urinary calcium loss. However, the magnitude of excretory calcium losses is significantly greater in DS rats and is potentiated by chemical sympathectomy in both strains. 2. We hypothesized that a defect in vitamin D metabolism may underlie the observed strain-dependent differences in calcium balance. 3. Arterial blood pressure (ABP), water and mineral balance and serum concentrations of 1,25-dihydroxyvitamin D3 (1,25(OH)2 D3) and 25-hydroxyvitamin D3 (25(OH)D3) were measured in intact and chemically sympathectomized (6-hydroxydopamine; 6-OHDA) DS and DR rats after 8 weeks on a HSLK diet. 4. Chronic ingestion of this diet resulted in marked and moderate levels of hypertension in DS and DR rats, respectively. The hypertension was abated and eliminated by 6-OHDA in the DS and DR strains, respectively. Independent of treatment, DS rats had significantly higher urinary excretion of calcium and reduced intestinal absorption of the ion compared with DR rats. The DS rats had significantly higher serum levels of 1,25(OH)2 D3 and markedly lower serum levels of 25(OH)D3 than DR rats. Chemical sympathectomy tended to increase 1,25(OH)2 D3 and to decrease 25(OH)D3 levels in both strains. 5. These data indicate a genetic difference in vitamin D metabolism between DS and DR rats. The abnormally elevated levels of 1,25(OH)2 D3 in DS rats may be an appropriate compensatory response to excessive excretory calcium loss and reduced target organ sensitivity to the hormone and may, maladaptively, directly contribute to hypertension, by stimulating vascular smooth muscle contractility.

Improved cholecalciferol nutrition in rats is noncalcemic, suppresses parathyroid hormone and increases responsiveness to 1, 25-dihydroxycholecalciferol.

We examined how cholecalciferol (vitamin D) nutrition affected serum 25-hydroxycholecalciferol (25(OH)D) and 1, 25-dihydroxycholecalciferol (1,25(OH)(2)D). Rats were fed conventional diet (vitamin D, 4.5 IU/g, or 7 nmol/d) or the same diet plus 18 nmol/d of extra vitamin D for 3 wk. The extra vitamin D resulted in greater serum 25(OH)D (51 +/- 3, vs. control of 21 +/- 2 nmol/L), and kidney mRNA for vitamin D receptor [VDR mRNA] (P = 0. 026) and lower serum 1,25(OH)(2)D (72 +/- 16 vs. control of 161 +/- 10 pmol/L, P = 0.001), and parathyroid hormone (PTH) (89 +/- 4 vs. control of 160 +/- 15 ng/L, P = 0.001). Kidney VDR mRNA relative to GAPDH mRNA correlated inversely with serum 1,25(OH)(2)D (r = -0.714, P = 0.006). There were no differences in serum calcium, phosphate, alkaline phosphatase, or weight gain. Experiment 2 compared groups supplemented with 0.2, 2 or 20 nmol/d of vitamin D orally, or 20 nmol/d dermally to see how vitamin D nutrition influenced the response of 1,25(OH)(2)D to changes in diet calcium. Vitamin D did not affect urinary calcium or pyridinoline excretion, serum calcium, phosphate, vitamin D binding protein or alkaline phosphatase. In groups given 20 nmol/d of vitamin D, renal mitochondrial 25(OH)D-1alpha-hydroxylase was lower (P < 0.01) and 25(OH)D-24-hydroxylase was higher (P < 0.05). Higher 25(OH)D concentration was related to proportionally lower 1,25(OH)(2)D at every calcium intake, indicating greater tissue sensitivity to 1, 25(OH)(2)D. We conclude suppression of 1,25(OH)(2)D and PTH, and higher renal VDR mRNA and 24-hydroxylase did not involve higher free 1,25(OH)(2)D concentration or a first pass effect at the gut. Thus, 25(OH)D or a metabolite other than 1,25(OH)(2)D is a physiological, transcriptionally and biochemically active, noncalcemic vitamin D metabolite.

Basal and stimulated ANF secretion: role of tissue preparation.

Our previous results showed that addition of agonists, such as vasopressin and angiotensin, added to incubation medium with freshly excised rat atria caused marked release of atrial natriuretic factor (ANF). This release was in the form of prohormone rather than active peptide. Since others had difficulty reproducing these findings, in the present study we investigated ANF release with and without angiotensin addition in two sets of atrial tissue. In the first, tissue was blotted and carefully cleaned as previously described; in the second, atrial tissue was placed into incubation medium without prior preparation. ANF activity in the medium was measured by radioimmunoassay and receptor assay. Using the immunoassay, basal release of ANF was threefold greater from prepared vs. nonprepared atrial tissue; significant stimulation by angiotensin was seen only in the prepared atria. ANF release measured by radioreceptor assay was 1/5-1/10 of that measured by immunoassay. Taking the difference between the two measurements as an index of prohormone secretion, the results confirm that both basal and stimulated release was primarily in the form of proANF. Scanning electron microscopy revealed that cleaning of the atria had removed the endocardial lining of the tissue. The results thus indicate that an intact endocardium can prevent agonist-induced proANF secretion, suggesting that this tissue may be an important modulator of plasma ANF levels.

In vitro secretion of atrial natriuretic factor: receptor-mediated release of prohormone.

Secretion of atrial natriuretic factor (ANF) in vivo is thought to be mediated by atrial distension. We have shown previously that nonstretched atria can release natriuretic activity in vitro when stimulated by certain agonists. In the present study atrial appendages from freshly excised rat hearts were incubated at 37 degrees C for up to 1 h in the presence of either vasopressin (5 X 10(-9) mol/l) or angiotensin II (2.5 X 10(-7) mol/l). Aliquots of postincubation media were injected intravenously into anesthetized bioassay rats to determine natriuretic activity. Control media, in which atria had been incubated without agonist, did not cause natriuresis. Significant increases in sodium excretion were seen after injection of media in which atria had been incubated in the presence of either agonist. Injection of medium with the same agonist concentration did not result in comparable natriuresis. Radioimmunoassay (RIA) indicated a high concentration of immunoactive ANF in the natriuretic media. However, radioreceptor assay (RRA) of the same media gave apparent ANF concentrations that were lower by about three orders of magnitude. Because the antibody used in the RIA cross reacts with ANF prohormone, whereas the RRA is sensitive only to the active form, we concluded that agonist-induced, stretch-independent release of ANF is in the form of prohormone, which can be converted to the active hormone in the circulation of the bioassay animal. The conclusion of prohormone release was confirmed by liquid chromatography. The data thus suggest that receptor-mediated as well as stretch-induced ANF secretion may be important in regulating the activity of the ANF system.

Renal responses to saline and atrial natriuretic factor infusions in Dahl rats.

Weanling Dahl rats of the salt-sensitive and salt-resistant strains were kept either on a low salt diet for 10-15 weeks, or the diet was supplemented with 7% NaCl for the last 30 days. Animals were anesthetized and the renal responses to acute saline infusion and infusion of synthetic atrial natriuretic factor (ANF) were studied on both dietary regimens. Arterial blood pressures of sensitive and resistant groups were not different on the low salt intake. As expected, addition of dietary salt increased pressure markedly in the sensitive animals. Resistant rats also had smaller, but statistically significant, increases in pressure. On the low salt diet, salt-sensitive rats showed a larger renal response to saline infusion, whereas on the high salt diet there were no significant differences between strains. The responses to ANF infusion were not different between groups on either diet, although NaCl feeding potentiated the natriuresis and diuresis. Under the conditions of the present experiments there was, therefore, no indication that Dahl salt-sensitive rats had a relative inability to respond either to an acute saline load or to exogenous ANF administration.

Cardiovascular effects of atrial extracts in anesthetized rats.

Tissue extracts derived from atria or ventricles of Sprague-Dawley rats were injected into Inactin-anesthetized assay rats. Compared with ventricular extracts, atrial extracts produced a 20 mmHg (1 mmHg = 133.322 Pa) fall in mean arterial blood pressure. This fall resulted from failure to increase cardiac output in compensation for peripheral vasodilation. Two factors were responsible: depression of heart rate (by 25 beats/min) and failure to increase cardiac performance. The time patterns and magnitudes of changes in cardiovascular parameters after cardiac extracts were not changed by prior atropinization. However, assay rats that were vagotomized showed no cardiac slowing after atrial extract and showed a significantly smaller decrease in mean arterial blood pressure than did sham-vagotomized or intact rats. Another group of assay rats was vagotomized as well as carotid-sinus-denervated before extract injection. In these rats the degree of hypotension caused by atrial extract was significantly greater than that observed after vagotomy alone and was not significantly different from that observed in rats with intact innervation. The results suggest that the hypotension that is caused by atrial extract, but not by ventricular extracts, results in part from the reflex effects of direct stimulation of chemosensitive cardiopulmonary receptors with vagal afferents and partly from the reflex effects of baroreceptor unloading. Ventricular extract had no hypotensive effect in any group of assay rats.

Multicentre study of effects of Org OD 14 on endometrium, vaginal cytology and cervical mucus in post-menopausal and oophorectomized women.

A multicentre study covering 69 post-menopausal or oophorectomized women was performed to determine whether Org OD 14 [7 alpha, 17 alpha)-17-hydroxy-7-methyl-19-norpregn-5(10)-en-20-yn-3-one) administered orally in a daily dose of 2.5 mg for 90 consecutive days induces endometrial proliferation. The treatment with Org OD 14 was continued in combination with 1 mg/day of lynestrenol from day 91 for 10 days to ascertain whether secretory transformation of the endometrium and subsequent withdrawal bleeding would occur. Endometrial biopsies were obtained before treatment and on day 91. The effects of Org OD 14 on vaginal mucosa and cervical mucus were also evaluated. Org OD 14 did not display any effect on the endometrium in 56 of the study subjects (83.5%). Weak stimulation (initial proliferation) was seen in 11 of the subjects (16.4%) and withdrawal bleeding occurred in only 5 of these after cessation of the combined treatment with lynestrenol. However, moderate 'oestrogenic' effects on vaginal mucosa and cervical mucus were induced in all study subjects.

Atrial natriuretic factor: reduced cardiac content in spontaneously hypertensive rats.

We recently discovered a potent natriuretic factor in cardiac atrial tissue. The present experiments were designed to determine whether hypertension was associated with altered tissue content of this atrial natriuretic factor. Extracts were prepared using fresh atria from spontaneously hypertensive rats of the Okamoto strain and from their Wistar-Kyoto controls. Two groups of anesthetized, normovolemic rats (Sprague-Dawley) were used to measure the renal natriuretic and chloriuretic effect of each type of extract. Results indicate that atrial content of natriuretic factor is reduced in hypertensive rats compared to control animals. We speculate that chronic release of the factor could have depleted atrial stores, and that increased blood levels of atrial natriuretic factor may be involved in the generation and maintenance of hypertension in this model.

Placebo-controlled cross-over study of effects of Org OD 14 in menopausal women.

A double-blind cross-over study with Org OD 14 and placebo was performed in 82 menopausal patients presenting with hot flushes and associated symptoms. Patients were randomly allocated to Org OD 14 or placebo as first treatment, and switched to placebo or Org OD 14 as second treatment. Each treatment period lasted for 16 weeks; no wash-out period was introduced. Tablets containing 2.5 mg of Org OD 14 or matched placebo tablets were supplied. Data on the following variables were obtained and analysed by the non-parametric randomization test for paired observations: hot flushes, sweating, dizziness, palpitations, fatiguability, headache, sleeplessness, irritability, breathlessness, backache and loss of libido and, in 16 patients, on circulating levels of FSH, LH, PRL, T3, T4, cortisol (F), SHBG, TBG and CBG. Twenty patients (13 placebo, 7 Org OD 14) withdrew, because their symptoms did not improve and one patient withdrew for reasons unrelated to treatment, so that 61 patients completed the study. The data demonstrated a good clinical effect and statistically significant differences in favour of Org OD 14 for hot flushes and a number of associated symptoms. Many patients reported on a general feeling of well being and a mood-elevating effect following Org OD 14. Org OD 14 significantly suppressed FSH and LH levels, while those of PRL remained unchanged. Although there was slight suppression of TBG and T4 which attained statistical significance, there was no influence on the most important parameter, T3. SHBG levels were slightly suppressed, whereas F and CBG levels were unaffected.

The treatment of postmenopausal vaginal atrophy with Ovestin vaginal cream or suppositories: clinical, endocrinological and safety aspects.

Seventy-four postmenopausal women presenting with vaginal atrophy were treated with either Ovestin vaginal cream (Group A, 23 women: 1 mg/day E3; Group B, 30 women: 0.5 mg/day E3) or vaginal suppositories (Group C, 21 women: 0.5 mg/day E3), applied daily for 3 wk (A and B) or 2 wk (C) before retiring. Ten women from A and 10 from B applied a maintenance dose (1 application twice weekly) during wk 4-16. Effects on vaginal cytology, cervical mucus and clinical and colposcopic findings were studied. Endometrial biopsies were done in 16 patients (A) before and after 3 wk of treatment, and, in 8 of the cases, at 16 wk. A routine laboratory screening program was performed before and after 16 wk of treatment in 10 patients (A). Plasma samples for hormone level determinations were obtained in 32 patients. Clinical and colposcopic findings showed a beneficial effect of treatments, confirmed by vaginal smears, and persisting during maintenance therapy. Effect on cervical mucus was slight to moderate. No side effects occurred and tolerance was very good. Endometrium remained atrophic under treatment. Screening program revealed no abnormalities. Treatments induced a sharp rise in plasma E3, followed by a gradual decline. Gonadotropins were slightly suppressed. E1, E2, PRL and SHBG capacity remained unchanged.

Characterization of the natriuretic activity in the plasma of hypervolaemic rats.

1. Plasma from hypervolaemic rats was fractionated on a G-200 Sephadex column. In addition to three different protein peaks, a fourth non-protein fraction was obtained. Each of the four peaks was desalted, freeze-dried, reconsituted and injected into normal anaesthetized rats. Significant natriuretic responses resulted, from injection, of the middle protein peak and of the small-molecular-weight peak. It was concluded that a natriuretic humoral factor was present in the blood of hypervolaemic rats, and that this factor was of low molecular weight but normally occurred bound to plasma protein. 2. The renal response to injection of non-protein fraction, obtained from either hypervolaemic donors or from iso- or hypo-volaemic donors, was compared in two groups of bioassay rats to test whether the natriuretic factor was present only in plasma of the blood-volume-expanded animals. Both types of reconstituted fraction caused diuresis, natriuresis and kaliuresis in bioassay animals. Only the natriuretic response was statistically greater when the fraction obtained from hypervolaemic plasma was used. In addition to non-specific increase in fluid and ion excretion, possibly due to the extraction and/or methodological procedures, these results demonstrate that blood-volume expansion releases a humoral natriuretic factor into plasma. Since there were no increases in filtration rate, the factor specifically inhibited tubular sodium reabsorption. 3. To determine the maximum possible effect of the non-protein factor, the dose given to bioassay rats was tripled. There was no further increase in sodium excretion, indicating that the effect was quantitatively limited and suggesting that the physiological importance of natriuretic hormone lies in long-term regulation of body-fluid balance.

Plasminogen activator levels in plasma and urine during exercise and oral contraceptive use.

The effect of Demulen (ethinyl estradiol 0.05 mg and ethynodiol diacetate 1 mg) and exercise on the level of plasminogen activators was studied in 25 women (12 controls and 13 contraceptive users). Plasma plasminogen activator level was increased by the use of the oral contraceptive and further increased by exercise. Urine plasminogen activator level was unchanged by the use of Demulen but, in both groups of subjects, was decreased by exercise.

Hemostatic changes induced by exercise during oral contraceptive use.

Exercise-induced changes in hemostatic measurements were studied in 25 women. Twelve of the subjects were not using oral contraceptives and the remainder were using Demulen (ethynodiol diacetate (1 mg) and ethinyl estradiol (0.05 mg)). Exercise on a treadmill induced similar changes in both groups, but during the use of Demulen the levels of fibrinogen and plasminogen were higher, antithrombin level was lower, and the recalcified clotting and dilute whole blood lysis times were shorter in group 2 than in the corresponding samples obtained from the nonpill users.

[Abortion as a socio-medical problem (author's transl)]. / Abortus kao socijalno-medicinski problem u nas.

PIP: This paper deals with the sociomedical problem of abortion in Yugoslavia. It describes conditions in the Socialist Republic of Serbia along with the latest data on the situation in the whole country. The authors maintain that this complex problem should be considered in its entirety, both retrospectively and prospectively, within the context of the socioeconomic development of our country. The evolution of this problem in time is given by development stages. (author's)^ieng