Effects of severe hemorrhage on plasma ANP and glomerular ANP receptors

Atrial natriuretic peptide (ANP) plays an important role in blood volume and electrolyte homeostasis in normovolemia and in hypervolemic states. The currently available information on the effects of hypovolemia on plasma ANP is contradictory. Moreover, possible regulation of ANP receptors during severe hemorrhagic hypovolemia has not been investigated. This study evaluated the effects of severe hemorrhage on plasma ANP and on the regulation of glomerular ANP receptor subtypes in anesthetized rats. Constant rate bleeding of 50% of total blood volume within 2 h induced a reproducible shock state characterized by marked decreases in blood pressure, heart rate, and hematocrit and an increase in plasma renin activity and aldosterone. Hemorrhaged rats exhibited a gradual significant increase in plasma ANP from 39.3 +/- 2.9 to 114.7 +/- 20.0 pmol/l 1 h after the bleeding (P < 0.001 from the initial value and P < 0.02 from the final value of sham-shock rats). Hemorrhage induced a significant decrease in total glomerular ANP binding sites (172 +/- 25 vs. 363 +/- 39 fmol/mg protein in hemorrhaged and sham-shock rats, respectively, P < 0.05). This decrease was mainly due to a significant decrease in ANPC receptors (132 +/- 22 vs. 312 +/- 40 fmol/mg protein in hemorrhaged and sham-shock rats, respectively, P < 0.05). Hemorrhage did not change glomerular ANPA receptor density. No significant differences in the affinity of the glomerular receptor subtypes for ANP were detected. Our data indicate that plasma ANP increases after prolonged severe hemorrhage. It is suggested that downregulation of renal ANPC receptors leads to reduced clearance of ANP and contributes to elevation of its plasma level after severe hemorrhage.

Regulation of renal glomerular and papillary ANP receptors in rats with experimental heart failure

Rats with aortocaval (A-V) fistula, an experimental model of congestive heart failure (CHF), display high circulating atrial natriuretic peptide (ANP) levels and a markedly blunted natriuretic response to ANP infusion. The present study was designed to evaluate whether alterations in renal ANP receptors may contribute to renal hyporesponsiveness to ANP in experimental CHF. Densities (Bmax) and dissociation constants (Kd) of both the biologically active (ANPA) and clearance receptors (ANPC) were evaluated in glomerular and papillary membranes from A-V fistula rats (n = 18) and sham-operated controls (n = 20). ANPA and ANPC receptor subtypes were assayed by displacement of 125I-ANP-(99-126) bound to glomerular or papillary membranes by increasing concentrations of unlabeled ANP-(99-126) or des-(18-22)-ANP-(4-23), an analogue which binds only to ANPC. Seven days after the operation, rats with A-V fistula displayed avid sodium retention, elevated plasma renin activity, and approximately a 10-fold increase in plasma ANP levels. Bmax of total ANP binding sites was significantly decreased in rats with A-V fistula compared with controls (220 +/- 61 vs. 399 +/- 88 fmol/mg protein, P < 0.05). The decrease was mainly due to a reduction in ANPA receptor density (51 +/- 10 vs. 110 +/- 15 fmol/mg protein, P < 0.05) with no change in receptor affinity. Likewise, a significant reduction in the density of ANPA (23 +/- 5 vs. 64 +/- 10 fmol/mg protein, P < 0.05) with no change in receptor affinity was observed in papillary membranes of rats with A-V fistula.(ABSTRACT TRUNCATED AT 250 WORDS)

What can be achieved in an external quality-assessment scheme with a small number of participants: four years of experience with thyroid-related tests in Israel

The Israel External Quality-Assessment scheme (EQAS) provided service from 1985 to 1989, primarily to laboratories in Israel. Participation was voluntary and confidential, and involved 30-35 laboratories performing thyroid-related function tests. Scheme design included 36 human serum specimens distributed to the participants at the beginning of each year. For 12 months, three specimens were analyzed each month and the results were reported to EQAS on pre-agreed dates. Monthly reports sent by EQAS to participants after analysis of the results included the overall consensus mean used as target value, between-laboratory agreement, individual laboratory bias, and recovery data. The overall consensus mean calculated as all-laboratory trimmed mean was validated by reproducibility and recovery studies. Samples with undetectable concentrations of thyrotropin (TSH), obtained from patients proven thyrotoxic, were used to validate measurement of very low TSH concentrations. During the scheme, liquid serum was found superior to lyophilized specimens for distribution to the participants. The scheme helped stimulate major improvements in between-laboratory agreement, especially for low TSH concentrations, with CVs decreasing from 180% in the first year to 20% in the fourth year. Each laboratory's performance also improved as judged by the median bias and variability of bias and by the considerable decrease in the number of laboratories with unacceptable performance for all tests. Method-related differences in performance were observed despite the small number of participants. Better methods, e.g., a radioimmunometric method for TSH, were detected and adopted by the participants, with concomitant improvement in performance. Transfer to analog procedures for free thyroxin, in addition to, but mostly instead of, thyroxin, was also documented, with no gain in analytical performance. Despite this being a small scheme, most of the goals achievable with a large scheme were realized.

What can be achieved in an external quality-assessment scheme with a small number of participants: four years of experience with thyroid-related tests in Israel

The Israel External Quality-Assessment scheme (EQAS) provided service from 1985 to 1989, primarily to laboratories in Israel. Participation was voluntary and confidential, and involved 30-35 laboratories performing thyroid-related function tests. Scheme design included 36 human serum specimens distributed to the participants at the beginning of each year. For 12 months, three specimens were analyzed each month and the results were reported to EQAS on pre-agreed dates. Monthly reports sent by EQAS to participants after analysis of the results included the overall consensus mean used as target value, between-laboratory agreement, individual laboratory bias, and recovery data. The overall consensus mean calculated as all-laboratory trimmed mean was validated by reproducibility and recovery studies. Samples with undetectable concentrations of thyrotropin (TSH), obtained from patients proven thyrotoxic, were used to validate measurement of very low TSH concentrations. During the scheme, liquid serum was found superior to lyophilized specimens for distribution to the participants. The scheme helped stimulate major improvements in between-laboratory agreement, especially for low TSH concentrations, with CVs decreasing from 180% in the first year to 20% in the fourth year. Each laboratory's performance also improved as judged by the median bias and variability of bias and by the considerable decrease in the number of laboratories with unacceptable performance for all tests. Method-related differences in performance were observed despite the small number of participants. Better methods, e.g., a radioimmunometric method for TSH, were detected and adopted by the participants, with concomitant improvement in performance. Transfer to analog procedures for free thyroxin, in addition to, but mostly instead of, thyroxin, was also documented, with no gain in analytical performance. Despite this being a small scheme, most of the goals achievable with a large scheme were realized.

Carcinoembryonic-like substance in breast fluid discharge in benign and malignant breast disease and in milk of lactating women

In a search for a simple noninvasive test for early detection of breast cancer, radioimmunoassay was used to determine carcinoembryonic (CEA) levels in the serum and breast fluid of 26 women presenting with spontaneous breast discharge, and in the serum and milk of 34 postpartum lactating women. In 54 milk samples from 34 healthy nursing mothers, the mean CEA level was 62.6 +/- 49.2 ng/ml (mean +/- SD) (range 5 to 252 ng/ml). The highest levels were found during the first days after delivery. Serum CEA levels measured in 18 of the 34 mothers were negative in 12 cases and normal (10 +/- 5.3 ng/ml) in six. No correlation was found between CEA levels in milk and those in serum. In the women with spontaneous breast fluid discharge, CEA levels in the breast fluid measured less than 300 ng/ml in 10 cases, 300 to 1,000 ng/ml in 9 cases and greater than 1,000 ng/ml in 7 cases. None of the 19 women with CEA values below 1,000 ng/ml had a malignancy. Four of the seven women with the highest CEA levels were found to have breast cancer. Serum CEA levels were within the normal range in both the malignant and nonmalignant cases. We conclude that CEA levels are markedly elevated in breast fluid discharges in nonlactating women, and that the highest levels may be associated with malignancy.

Assessment of fetal lung maturity by a microviscosimeter

A new method of rapid antenatal assessment of fetal lung maturity was evaluated in relation to the newborn outcome and two other accepted test. This method is based on fluorescence depolarization (FD) technique. The special instrumentation required for this method (the Microviscosimeter) was found to be simple and easy to handle even to nonprofessional personnel. Analysis of 47 samples of amniotic fluid received within 48 hours of delivery demonstrated that lung maturity threshold may be related to a numeric value (P value) measured by this technique. With a P value of less than 0.320 respiratory distress syndrome (RDS) is unlikely to develop. With a P value greater than 0.340, chances for RDS, usually severe, are high. With a P value of less than 0.340 but greater than 0.320, RDS may or may not develop. This method did not prove to be more reliable then the determination of L/S ratio by thin layer chromatography, but its advantage is that it supplies the results in less then an hour. The FD technique proved to be more reliable then the commonly used foam stability test.