Haplosufficient genomic androgen receptor signaling is adequate to protect female mice from induction of polycystic ovary syndrome features by prenatal hyperandrogenization.

Polycystic ovary syndrome (PCOS) is associated with reproductive, endocrine, and metabolic abnormalities. Because hyperandrogenism is the most consistent PCOS feature, we used wild-type (WT) and androgen receptor (AR) knockout (ARKO) mice, together with a mouse model of PCOS, to investigate the contribution of genomic AR-mediated actions in the development of PCOS traits. PCOS features were induced by prenatal exposure to dihydrotestosterone (250 µg) or oil vehicle (control) on days 16-18 of gestation in WT, heterozygote, and homozygote ARKO mice. DHT treatment of WT mice induced ovarian cysts (100% vs 0%), disrupted estrous cycles (42% vs 100% cycling), and led to fewer corpora lutea (5.0±0.4 vs 9.8±1.8). However, diestrus serum LH and FSH, and estradiol-induced-negative feedback as well as hypothalamic expression of kisspeptin, neurokinin B, and dynorphin, were unaffected by DHT treatment in WT mice. DHT-treated WT mice exhibited a more than 48% increase in adipocyte area but without changes in body fat. In contrast, heterozygous and homozygous ARKO mice exposed to DHT maintained comparable ovarian (histo)morphology, estrous cycling, and corpora lutea numbers, without any increase in adipocyte size. These findings provide strong evidence that genomic AR signaling is an important mediator in the development of these PCOS traits with a dose dependency that allows even AR haplosufficiency to prevent induction by prenatal androgenization of PCOS features in adult life.

Characterization of reproductive, metabolic, and endocrine features of polycystic ovary syndrome in female hyperandrogenic mouse models.

Polycystic ovary syndrome (PCOS) affects 5-10% of women of reproductive age, causing a range of reproductive, metabolic and endocrine defects including anovulation, infertility, hyperandrogenism, obesity, hyperinsulinism, and an increased risk of type 2 diabetes and cardiovascular disease. Hyperandrogenism is the most consistent feature of PCOS, but its etiology remains unknown, and ethical and logistic constraints limit definitive experimentation in humans to determine mechanisms involved. In this study, we provide the first comprehensive characterization of reproductive, endocrine, and metabolic PCOS traits in 4 distinct murine models of hyperandrogenism, comprising prenatal dihydrotestosterone (DHT, potent nonaromatizable androgen) treatment during days 16-18 of gestation, or long-term treatment (90 days from 21 days of age) with DHT, dehydroepiandrosterone (DHEA), or letrozole (aromatase inhibitor). Prenatal DHT-treated mature mice exhibited irregular estrous cycles, oligo-ovulation, reduced preantral follicle health, hepatic steatosis, and adipocyte hypertrophy, but lacked overall changes in body-fat composition. Long-term DHT treatment induced polycystic ovaries displaying unhealthy antral follicles (degenerate oocyte and/or > 10% pyknotic granulosa cells), as well as anovulation and acyclicity in mature (16-week-old) females. Long-term DHT also increased body and fat pad weights and induced adipocyte hypertrophy and hypercholesterolemia. Long-term letrozole-treated mice exhibited absent or irregular cycles, oligo-ovulation, polycystic ovaries containing hemorrhagic cysts atypical of PCOS, and displayed no metabolic features of PCOS. Long-term dehydroepiandrosterone treatment produced no PCOS features in mature mice. Our findings reveal that long-term DHT treatment replicated a breadth of ovarian, endocrine, and metabolic features of human PCOS and provides the best mouse model for experimental studies of PCOS pathogenesis.

SynGAP isoforms exert opposing effects on synaptic strength.

Alternative promoter usage and alternative splicing enable diversification of the transcriptome. Here we demonstrate that the function of Synaptic GTPase-Activating Protein (SynGAP), a key synaptic protein, is determined by the combination of its amino-terminal sequence with its carboxy-terminal sequence. 5' rapid amplification of cDNA ends and primer extension show that different N-terminal protein sequences arise through alternative promoter usage that are regulated by synaptic activity and postnatal age. Heterogeneity in C-terminal protein sequence arises through alternative splicing. Overexpression of SynGAP α1 versus α2 C-termini-containing proteins in hippocampal neurons has opposing effects on synaptic strength, decreasing and increasing miniature excitatory synaptic currents amplitude/frequency, respectively. The magnitude of this C-terminal-dependent effect is modulated by the N-terminal peptide sequence. This is the first demonstration that activity-dependent alternative promoter usage can change the function of a synaptic protein at excitatory synapses. Furthermore, the direction and degree of synaptic modulation exerted by different protein isoforms from a single gene locus is dependent on the combination of differential promoter usage and alternative splicing.

Combining cariporide with glyceryl trinitrate optimizes cardiac preservation during porcine heart transplantation.

Sodium-hydrogen exchange inhibitors, such as cariporide, are potent cardioprotective agents, however, safety concerns have been raised about intravenously (i.v.) administered cariporide in humans. The aim of this study was to develop a preservation strategy that maintained cariporide's cardioprotective efficacy during heart transplantation while minimizing recipient exposure. We utilized a porcine model of orthotopic heart transplantation that incorporated donor brain death and 14 h static heart storage. Five groups were studied: control (CON), hearts stored in Celsior; CAR1, hearts stored in Celsior with donors and recipients receiving cariporide (2 mg/kg i.v.) prior to explantation and reperfusion, respectively; CAR2, hearts stored in Celsior supplemented with cariporide (10 mumol/L); GTN, hearts stored in Celsior supplemented with glyceryl trinitrate (GTN) (100 mg/L); and COMB, hearts stored in Celsior supplemented with cariporide (10 mumol/L) plus GTN (100 mg/L). A total of 5/5 CAR1 and 5/6 COMB recipients were weaned from cardiopulmonary bypass compared with 1/5 CON, 1/5 CAR2 and 0/5 GTN animals (p = 0.001). Hearts from the CAR1 and COMB groups demonstrated similar cardiac function and troponin release after transplantation. Supplementation of Celsior with cariporide plus GTN provided superior donor heart preservation to supplementation with either agent alone and equivalent preservation to that observed with systemic administration of cariporide to the donor and recipient.

Subfertile female androgen receptor knockout mice exhibit defects in neuroendocrine signaling, intraovarian function, and uterine development but not uterine function.

Female androgen receptor (AR) knockout mice (AR(-/-)) generated by an in-frame Ar exon 3 deletion are subfertile, but the mechanism is not clearly defined. To distinguish between extra- and intraovarian defects, reciprocal ovarian transplants were undertaken. Ovariectomized AR(-/-) hosts with wild-type (AR(+/+)) ovary transplants displayed abnormal estrus cycles, with longer cycles (50%, P < 0.05), and 66% were infertile (P < 0.05), whereas AR(+/+) hosts with either AR(-/-) or surgical control AR(+/+) ovary transplants displayed normal estrus cycles and fertility. These data imply a neuroendocrine defect, which is further supported by increased FSH (P <0.05) and estradiol (P <0.05), and greater LH suppressibility by estradiol in AR(-/-) females at estrus (P <0.05). Additional intraovarian defects were observed by the finding that both experimental transplant groups exhibited significantly reduced pups per litter (P < 0.05) and corpora lutea numbers (P < 0.05) compared with surgical controls. All groups exhibited normal uterine and lactation functions. AR(-/-) uteri were morphologically different from AR(+/+) with an increase in horn length (P < 0.01) but a reduction in uterine diameter (P < 0.05), total uterine area (P < 0.05), endometrial area (P < 0.05), and myometrial area (P < 0.01) at diestrus, indicating a role for AR in uterine growth and development. Both experimental transplant groups displayed a significant reduction in uterine diameter (P < 0.01) compared with transplanted wild-type controls, indicating a role for both AR-mediated intraovarian and intrauterine influences on uterine physiology. In conclusion, these data provide direct evidence that extraovarian neuroendocrine, but not uterine effects, as well as local intraovarian AR-mediated actions are important in maintaining female fertility, and a disruption of AR signaling leads to altered uterine development.

Polymorphonuclear leukocyte phagocytic function increases in plasminogen knockout mice.

BACKGROUND: Mice lacking plasminogen (PG-/-) require alternative pathways of fibrinolysis for survival. This may depend on polymorphonuclear leukocytes (PMN) that can clear soluble and insoluble fibrin(ogen) through PG-independent processes. Our objective was to demonstrate that PMNs from PG-/- mice exhibit increased Mac-1 dependent phagocytic activity, which may explain their increased fibrin(ogen)lytic activity compared with wild type (PG+/+) mice. METHODS: Phagocytic activity of PMNs from PG-/- and PG+/+ mice was compared following exposure to Staphylococcus aureus (S. aureus) particles and the expression of Mac-1 was assessed in parallel by flow cytometric analysis. Resistance to phorbol-12-myristate-13-acetate (PMA)-induced cell death was compared between PMNs from the different genotypes. RESULTS: Stimulation of PG-/- PMNs by opsonized S. aureus diluted in PG-/- plasma significantly increased phagocytosis (15-fold) compared with stimulation of PG+/+ PMNs in PG+/+ plasma. Incubation of PG-/- PMNs with PG+/+ plasma (control) or PG-/- plasma supplemented with human PG inhibited this increased phagocytic activity. Mac-1 cell surface density increased 6.2+/-1.0-fold in PG-/- PMNs versus 2.9+/-0.6-fold in PG+/+ PMNs (P < 0.01) indicating that Mac-1 may be associated with increased phagocytic activity. Supporting this, treatment of PG-/- PMNs with an anti-Mac-1 antibody in PG-/- plasma inhibited phagocytic activity. In addition, physiologic PG blocked Mac-1 accessibility at the surface of PMNs. Addition of PMA resulted in 33% death of PMNs from PG-/- mice versus 68% in PG+/+ controls (P < 0.001). CONCLUSIONS: PMNs from PG-/- mice exhibit a Mac-1 dependent increase in phagocytic activity that is suppressed with human PG, an anti-Mac-1 antibody or the plasma from PG+/+ mice. The propensity for PMNs from PG-/- mice to be activated in response to PMA together with their relative resistance to PMA-toxicity may contribute to increased PMN half-life and enhanced fibrin(ogen) clearance in the setting of PG deficiency.

sICAM-1 measurements are independent of processing method and sampling site in patients with coronary artery disease.

sICAM-1 measurements are here shown to be independent of processing method (serum, platelet rich and platelet poor plasma) and sampling size (venous or arterial blood) in patients with coronary disease.

Particulate debris collected during carotid stenting: are we missing something?

Particulate and histopathologic examination of atherosclerotic material collected during carotid artery stenting is presented, illustrating the limitations of current knowledge regarding the use of distal protection devices (DPD) during this novel vascular intervention.

Diastolic dysfunction and abnormality of the Na+/Ca2+ exchanger in single uremic cardiac myocytes.

Cardiovascular disease is the most common cause of death in patients with end-stage renal disease, possibly due to a specific "uremic cardiomyopathy". This study investigated the function of the Na(+)/Ca(2+) exchanger in single cardiac myocytes from a model of early renal impairment. Mild uremia was induced by partial (5/6) nephrectomy in male Wistar rats. After 4 weeks, ventricular myocytes were isolated, loaded with the fluorescent Ca(2+) indicator indo-1, and contractile function and calcium transients recorded following electrical pacing at 0.2 Hz. Relaxation from rapid cooling contractures (RCCs) was also studied. Cells from uremic animals (U) were hypertrophied compared with controls (C), with a significant increase in width (14%; P<0.02) and cross-sectional area (13%; P<0.03). There was a significant increase in diastolic intracellular Ca(2+) ratio in the uremic cells (C, 0.33+/-0.00 vs U, 0.37+/-0.02; P<0.02), although the amount of calcium released per twitch was similar. Uremic cells were slower to relax following RCCs, however when Na(+)/Ca(2+) exchange was inhibited using a Na(+)-free/Ca(2+)-free solution, this difference was abolished. Under these conditions, there was little difference in the relaxation rate of control cells, indicating that the Na(+)/Ca(2+) exchanger plays only a minor role in relaxation in normal rat myocytes. However in uremia, the data indicate that the Na(+)/Ca(2+) exchanger actively interfered with relaxation, possibly by working in reverse rather than forward mode. These results indicate that myocyte relaxation and Ca(2+) handling are abnormal in early uremia and may provide further evidence for the existence of a specific "uremic cardiomyopathy".

Animal models of atherosclerosis progression: current concepts.

The last decade has seen a number of important advances in the use of animal models of atherosclerosis progression. Small animal models, particularly mouse knockouts and rabbit models, are finding increasing use. This review discusses those models of particular research utility, highlights their advantages and limitations, and specifically addresses methodologies and current developments, in what is a rapidly changing field.

Plasma OLC is elevated in mild experimental uremia but is not associated with hypertension.

BACKGROUND: Little is known about the renal handling of endogenous ouabain-like compound (OLC). The aim of this study was to determine the normal renal clearance of OLC and the effect of mild experimental uremia on plasma OLC and its clearance. METHODS: Male Wistar rats were studied 8 weeks after subtotal (5/6th) nephrectomy (n = 8) and compared with a control sham-operated group (n = 8). RESULTS: Plasma creatinine and OLC were higher in uremic animals compared with controls (creatinine 76+/-5.6 micromol/L v 45+/-9.6 micromol/L, respectively, P < .00005; OLC 195+/-62 pmol/L v 121+/-62 pmol/L, P < .02). Creatinine clearance and OLC clearance were lower in uremic animals compared with controls (creatinine 1.06+/-0.12 mL/min v 1.58+/-0.32 mL/min, respectively, P < .002; OLC 23.6+/-10.4 microL/min v 33.2+/-11.4 microL/min, P < .05). There were no significant differences (all P > .05) between the uremic and control groups in the fractional clearance of OLC (uremic 2.3%+/-1.0% v control 2.2%+/-1.0%), OLC excretion rate (uremic 6.2+/-2.4 pmol/24 h v control 5.0+/-1.1 pmol/24 h) or in the mean systolic blood pressure (BP) (uremic 132+/-13 mm Hg v control 126+/-3 mm Hg). The amount of OLC excreted per unit of functioning nephron mass was 78% higher in uremic animals than in controls. The rate of tubular absorption varied linearly with filtered load, did not differ between groups, and showed no evidence of saturation. CONCLUSIONS: The kidneys are an important excretion route for plasma OLC and moderate but significant increases may occur without inducing hypertension in the short term. The low fractional clearance of OLC is most likely due to tubular absorption and/or catabolism.

L-type calcium current of isolated rat cardiac myocytes in experimental uraemia.

BACKGROUND: End-stage renal failure is associated with a low-output cardiomyopathy, left ventricular hypertrophy and increased QTc dispersion. Cardiac dysfunction is prevalent in patients at the beginning of dialysis and is an important predictor of mortality. Ca(2+) influx through voltage-gated L-type Ca(2+) channels plays a key role in the excitation-contraction coupling of cardiac myocytes. The purpose of this study was to examine the effect of subtotal nephrectomy (SNx) in the rat on both cardiac L-type Ca(2+) currents and action potential duration. METHODS: Wistar rats underwent two-stage SNx; control rats (C) underwent bilateral renal decapsulation. Animals were sacrificed after 8 weeks, and ventricular myocytes were isolated. SNx rats showed a 2-fold increase in plasma urea and creatinine compared with C rats. Whole-cell patch clamp techniques were used to examine L-type Ca(2+) channel currents in isolated cardiac myocytes at 37 degrees C. In separate experiments, the epicardial monophasic action potentials of isolated perfused whole hearts from C and SNx rats were recorded. RESULTS: The amplitude and current-voltage relationships of the L-type Ca(2+) current were not significantly different in myocytes from C (n=11) and SNx (n=8) rats. However, the rate of inactivation of the Ca(2+) current was increased by approximately 15-25% (P<0. 05) in myocytes from SNx rats. The action potential duration (APD(33)) at the apex of the left ventricle was approximately 20% shorter (P<0.01) in hearts from SNx rats as compared with controls. CONCLUSIONS: Renal failure is associated with rapid inactivation of cardiac ventricular myocyte L-type Ca(2+) currents, which may reduce Ca(2+) influx and contribute to shortening of the action potential duration.

Ramipril prevents basal arterial constriction and enhanced myogenic tone in the femoral artery in mildly uraemic normotensive rats.

Some aspects of vascular reactivity are altered in mild experimental uraemia, as shown by increased myogenic tone and a reduced lumen diameter in the femoral artery. This study was conducted to investigate the prevention of these uraemia-induced vascular abnormalities by the angiotensin-converting enzyme inhibitor (ACE-I) Ramipril. Ten male Wistar rats were rendered uraemic (U) by 5/6th nephrectomy, and 10 control (C) rats were concurrently sham-operated. After 4 weeks, both groups were given daily subcutaneous injections of 3 microg of Ramipril for a further 4 weeks. Tail-cuff systolic blood pressure was then recorded and the rat was killed. Isolated femoral arteries were mounted on a pressure myograph and pressurized at 40 mmHg for baseline measurements of the lumen internal diameter. Myogenic tone was then assessed over a range of intravascular pressures from 40 to 160 mmHg. Biochemically, serum urea and creatinine were significantly higher in the uraemic (U) group [urea: U, 23+/-3 mmol/l; C, 6+/-1 mmol/l (P<0.001); creatinine: U, 147+/-17 mmol/l, C, 72+/-11 mmol/l (P<0.01)]. Systolic blood pressure was the same in both groups (U, 127+/-7 mmHg; C, 127+/-3 mmHg). The mean baseline internal diameter was the same in both groups (U, 756+/-22 microm; C, 721+/-34 microm, not significant), as was mean myogenic tone (U, 4.7+/-1%; C, 3.4+/-1%). In conclusion, there were no differences in baseline lumen diameter or myogenic tone in uraemic compared with control femoral arteries of rats treated with Ramipril, which suggests that Ramipril may prevent the development of elevated myogenic tone and decreased lumen diameter previously observed in this model of uraemia. These results suggest that these specific vascular abnormalities in uraemia may be mediated by renin or bradykinin, or by the direct action of angiotensin II on vascular smooth muscle.

Increased myogenic tone precedes structural changes in mild experimental uraemia in the absence of hypertension in rats.

1. Mechanical forces associated with blood flow play important roles in the acute control of vascular tone, the regulation of arterial structure and remodelling and the localization of atherosclerotic plaque. Uraemia is a proatherogenic process and is expected to be associated with impaired vascular reactivity.2. To study this, 12 male Wistar rats were rendered uraemic by five-sixths nephrectomy and 12 control rats were sham operated simultaneously. After 8 weeks a tail-cuff systolic blood pressure was recorded, blood samples were taken and the animals killed. Isolated femoral arteries were dissected and mounted on a pressure myograph and myogenic tone was assessed over a range of intravascular pressures from 40 to 160 mmHg. Histologically the arteries were comparatively examined for gross morphology, calcification and deposition of collagen.3.Biochemically the serum urea and creatinine were greater in the uraemic compared with the control rats (urea: 23.5+/-6 mmol/l and 6.8+/-01 mmol/l respectively, P not significant; creatinine: 130.7+/-13 mmol/l and 70.3+/-5 mmol/l respectively, P<0.01) but systolic blood pressure was the same in both groups (control, 97+/-1 mmHg; uraemic, 98+/-2 mmHg), compatible with mild uraemia.4. Myogenic tone was significantly greater in uraemic vessels (7.3+/-1.8% versus 2.3+/-0. 4% in control, P=0.01). The actual vessel lumen diameter was also smaller in pressurized uraemic vessels compared with control vessels (471+/-30 microm versus 604+/-33 microm, P<0.01) after equilibration in physiological salt solution. However, when incubated in calcium-free physiological salt solution, the passive internal diameter was similar in uraemic vessels (538+/-25 microm compared with 595+/-31 microm in control). Histologically, there were no differences between the two groups.5. We conclude that some aspects of vascular reactivity are altered in mild experimental uraemia as shown by a reduced internal lumen diameter and increased myogenic tone. Furthermore, these changes are apparent in the absence of hypertension and precede structural changes.

Contractile dysfunction of isolated ventricular myocytes in experimental uraemia.

In order to clarify the mechanism underlying impaired cardiac performance in uraemia, the contractile function of isolated cardiac myocytes from chronically uraemic and control rats has been compared. Rats were made uraemic by sub-total nephrectomy in a two-stage surgical procedure, and left for 4 weeks. Sham-operated controls were prepared at the same time. Animals were pairfed, and final body weights were not significantly different between the groups. Ventricular myocytes were isolated and their contraction amplitude and velocity were measured using a video-based edge-detection system. Contraction was depressed in myocytes from uraemic animals, with contraction amplitude in maximum Ca2+ reduced from 16.3 +/- 0.6% shortening, to 13.0 +/- 0.8% (p < 0.01, n = 10 animals for each group). There was a concomitant decrease in the velocity of shortening (5.6 +/- 0.4 vs. 3.9 +/- 0.5 micron s-1 change in sarcomere length, p < 0.02) and of relaxation (4.6 +/- 0.4 vs. 3.2 +/- 0.4 micron s-1 p < 0.02). Similar depression was seen at lower perfusate Ca2+ concentrations (1-2 mM) and the EC50 for Ca2+ was unchanged. The response to beta-adrenoceptor stimulation was decreased by the same magnitude as that to Ca2+, with no change in the EC50 for isoproterenol or the ratio of maximum response to isoproterenol or to Ca2+ in the same cell (isoproterenol/Ca2+ ratio). There was no shift in the myosin isozyme composition in uraemic cells, with both groups showing a heterogeneous V1/V2/V3 pattern. We conclude that chronic uraemia is associated with a depression of contractile function in the isolated myocyte but no shift in myosin isoforms or specific beta-adrenoceptor desensitisation.

Recombinant erythropoietin increases blood pressure in experimental hypertension and uraemia without change in vascular cytosolic calcium.

The mechanism of erythropoietin-induced hypertension in dialysis patients is unclear. Intracellular calcium ([Ca2+]i) may be altered in both hypertension and uraemia, and the effects of both uraemia and r-HuEPO on vascular smooth muscle [Ca2+]i and blood pressure (BP) in Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) were therefore studied. Male WKY and SHR underwent partial nephrectomy or sham operation. Three weeks later a 28-day period of treatment with either r-HuEPO 100 U/kg, s.c., 3 times/week or buffer was commenced (n = 10-12 for each subgroup). BP was measured weekly, by noninvasive Doppler tail-cuff assessment. [Ca2+]i was measured following loading with fura-2 in pooled, primary aortic vascular smooth muscle cells (VSMC). Serum urea and creatinine rose 3- to 4-fold after partial nephrectomy. Treatment with r-HuEPO did not change renal function further in either uraemic or control WKY or SHR. Haemoglobin increased in both non-uraemic WKY (16.2-20.3 g/dl) and SHR (16.4-20.5 g/dl) and uraemic animals (WKY 13.9-20.9; SHR 13.8-18.8 g/dl; p < 0.01 for all changes) following 4 weeks of r-HuEPO treatment. BP was unaffected by r-HuEPO in WKY but increased in nonuraemic SHR (210-250; p < 0.01) and in uraemic SHR (224-251 mm Hg; p < 0.001) at 4 weeks. VSMC [Ca2+]i was higher in SHR than WKY (121 vs. 83 nmol/l; MANOVA p < 0.05) but no effect of uraemia or r-HuEPO on [Ca2+]i was detected. In conclusion, the hypertensive effects of r-HuEPO are augmented both in a genetic model of hypertension and in uraemia. Although VSMC [Ca2+]i was elevated in SHR, the further increase in BP induced by r-HuEPO was not associated with alterations in VSMC cytosolic calcium.

Modulation of platelet cytosolic calcium during erythropoietin therapy in uraemia.

Erythropoietin therapy for uraemic anaemia is associated with a high rate of hypertensive and thrombotic complications. The mechanism is unknown, but a change in cellular calcium control may be relevant to changes in blood pressure and thrombosis. Platelets were utilized as a model of vascular smooth muscle cells. The effects of erythropoietin therapy on platelet cellular calcium, assessed by fura-2, were measured in 25 patients receiving renal replacement therapy during a 6-month treatment period. Three patients failed to reach a target haemoglobin and were excluded from the analysis. Blood pressure increased in 11 of the remaining 22 subjects, eight requiring an increase in antihypertensive medication. There were no differences in cellular calcium control between the group in whom blood pressure rose and patients with stable blood pressure. Overall there was a fall of 24% in resting cytosolic calcium (baseline 69.2 +/- 5.1 to 52.5 +/- 3.0 nmol/l, P < 0.05) after 3 months of erythropoietin therapy. There was no change in the thrombin-stimulated peak response in the presence of extracellular calcium during therapy, although thrombin-stimulated intracellular release also fell at 3 months (baseline 769 +/- 61 versus 3 months 559 +/- 49 nmol/l, P < 0.01). This study suggests that intracellular free calcium control within platelets improves in response to erythropoietin therapy. However these changes appear not to be related to the development of hypertension.

Platelet cytosolic free calcium concentration and parathyroid hormone: changing relationships with haemodialysis in end-stage renal disease.

1. Twelve patients receiving haemodialysis for end-stage renal failure were studied at a single dialysis session. Platelet cytosolic calcium concentration, plasma ionized calcium concentration and serum parathyroid hormone concentration were measured before dialysis, mid-dialysis and 30 min after dialysis. 2. Plasma ionized calcium concentration increased towards dialysate calcium concentrations, falling insignificantly after cessation of dialysis. Serum parathyroid hormone concentration fell by 39% during dialysis, with incomplete recovery afterwards. There was no overall change in platelet cytosolic calcium concentration. 3. Patients were divided into two subgroups: low parathyroid hormone (serum parathyroid hormone concentration less than 10 pmol/l) and high parathyroid hormone (serum parathyroid hormone concentration greater than 10 pmol/l). Before dialysis, values of platelet cytosolic calcium concentration or plasma ionized calcium concentration were not statistically different between the subgroups, but the platelet cytosolic calcium concentration was higher in the high-parathyroid hormone subgroup during and after dialysis. 4. Before haemodialysis there was a linear correlation between plasma ionized calcium concentration and platelet cytosolic calcium concentration, which disappeared during dialysis. In contrast, there was no relationship between serum parathyroid hormone concentration and platelet cytosolic calcium concentration before dialysis, but after dialysis a hyperbolic relationship was evident. 5. These results suggest that uraemic toxins may interfere with cytosolic calcium homoeostasis, allowing passive diffusion of extracellular calcium to influence the resting concentration, and that this effect is reversible by haemodialysis.

Evidence of non-maternally mediated acceleration of eye-opening in 'enriched' artificially reared rat pups.

Rat pups were artificially reared, without their mothers, from postnatal day 5. They were exposed thereafter to impoverished or enriched environmental conditions. The enrichment included gentling, social interaction and homing experience. Enriched rats showed accelerated eye-opening compared with their impoverished littermates (P less than 0.02). This is the first demonstration of stimulation-induced acceleration of development which cannot have been maternally mediated.