Effect of Continuous Trio Breeding Compared with Continuous Pair Breeding in 'Shoebox' Caging on Measures of Reproductive Performance in Estrogen Receptor Knockout Mice

Some performance standards for continuous trio breeding in 'shoebox' cages for inbred stocks and outbred strains of mice challenge the minimum floor space recommendations in the 8th edition of the Guide for the Care and Use of Laboratory Animals. In our study, we evaluated whether continuous trio breeding could be successfully applied to a breeding colony of genetically engineered mice housed in shoebox cages with a floor area of 67.6 in2. Mice heterozygous for genetically engineered mutations to estrogen receptors and their wildtype counterparts were continuously bred as trios or pairs. Confounding environmental factors were controlled through standardized husbandry practices and husbandry, and all mice were bred simultaneously to control for temporal factors. Several measures of reproductive performance-including number of litters per female, production index, interlitter interval, litter size at birth, litter size at weaning, weaning rate, and body weight of pups at weaning- were evaluated over approximately 6 mo. Regardless of genotype, interlitter interval, litter size at birth, and litter size at weaning were significantly lower for trio-bred mice than for pair-bred mice. In addition, significant interactions emerged between genotype and breeding strategy for these reproductive measures. Furthermore, significant differences between genotypes occurred for interlitter interval and weaning rate, regardless of breeding strategy. Underlying mechanisms to account for effects of genotype on interlitter interval and the interaction of genotype with breeding strategy were unclear but may reflect effects of overcrowding and reproductive suppression.

Refining timed pregnancies in two strains of genetically engineered mice

In order to efficiently generate genetically engineered mouse (GEM) fetuses or neonates of a specified age range, researchers must develop strain-specific strategies, including reliable early pregnancy detection. The authors evaluated pregnancy indices (pregnancy rate, plug rate, pregnant plugged rate, first litter size and body weight) in two GEM breeding colonies: homozygous soluble epoxide hydrolase knockout (sEHKO) mice (n=164 females) and L7-tau-green fluorescent protein (GFP) transgenic mice (n=61 females). The goals of the study were to determine the most accurate early pregnancy indicator and to reliably and cost-effectively produce timed pregnant females that were between gestation days 16 and 18. The authors set up each timed mating by placing two naturally synchronized females with a male for 48 h. When males were present, personnel checked each female daily for a vaginal plug. They then weighed the females immediately, 1 week and 2 weeks after removing the males. In both sEHKO and GFP colonies, increases in body weight at 1 and 2 weeks after timed male exposure more reliably and consistently indicated pregnancy than did plug detection. Further evaluations and protocol refinements are planned based on litter size and litter number in these colonies.

Injection of oxotremorine in nucleus accumbens shell reduces cocaine but not food self-administration in rats

Mesencephalic dopamine neurons form synapses with acetylcholine (ACh)-containing interneurons in the nucleus accumbens (NAcc). Although their involvement in drug reward has not been systematically investigated, these large aspiny interneurons may serve an important integrative function. We previously found that repeated activation of nicotinic cholinergic receptors enhanced cocaine intake in rats but the role of muscarinic receptors in drug reward is less clear. Here we examined the impact of local changes in muscarinic receptor activation within the NAcc on cocaine and food self-administration in rats trained on a progressive ratio (PR) schedule of reinforcement. Animals were given a minimum of 9 continuous days of drug access before testing in order to establish a stable breaking point (BP) for intravenous cocaine infusions (0.75 mg/kg/infusion). Rats in the food group acquired stable responding on the PR schedule within 7 days. On the test day, rats were bilaterally infused in the NAcc with the muscarinic receptor agonist oxotremorine methiodide (OXO: 0.1, 0.3 or 1 nmol/side), OXO plus the M(1) selective antagonist pirenzepine (PIRENZ; 0.3 nmol/side) or aCSF 15 min before cocaine or food access. OXO dose dependently reduced BP values for cocaine reinforcement (-17%, -44% [p<0.05] and -91% [p<0.0001] for 0.1, 0.3 and 1.0 nmol, respectively) and these reductions dissipated by the following session. Pretreatment with PIRENZ blocked the BP-reducing effect of 0.3 nmol OXO. Notably, OXO (0.1, 0.3 and 1.0 nmol/side) injection in the NAcc did not affect BP for food reward. The results suggest that muscarinic ACh receptors in the caudomedial NAcc may play a role in mediating the behavior reinforcing effects of cocaine.

Immunohistochemical and functional correlations of renal cyclooxygenase-2 in experimental diabetes

Prostaglandins (PGs) generated by the enzyme cyclooxygenase (COX) have been implicated in the pathological renal hemodynamics and structural alterations in diabetes mellitus, but the role of individual COX isoenzymes in diabetic nephropathy remains unknown. We explored COX-1 and COX-2 expression and hemodynamic responses to the COX-1 inhibitor valeryl salicylate (VS) or the COX-2 inhibitor NS398 in moderately hyperglycemic, streptozotocin-diabetic (D) and control (C) rats. Immunoreactive COX-2 was increased in D rats compared with C rats and normalized by improved glycemic control. Acute systemic administration of NS398 induced no significant changes in mean arterial pressure and renal plasma flow in either C or D rats but reduced glomerular filtration rate in D rats, resulting in a decrease in filtration fraction. VS had no effect on renal hemodynamics in D rats. Both inhibitors decreased urinary excretion of PGE(2). However, only NS398 reduced excretion of thromboxane A(2). In conclusion, we documented an increase in renal cortical COX-2 protein expression associated with a different renal hemodynamic response to selective systemic COX-2 inhibition in D as compared with C animals, indicating a role of COX-2-derived PG in pathological renal hemodynamic changes in diabetes.

Upregulation of G protein-linked receptor kinases with advancing age in rat aorta

The age-related decline in beta-adrenergic receptor (beta-AR)-mediated vasorelaxation is associated with desensitization of beta-ARs without significant downregulation. The primary mode of this homologous beta-AR desensitization, in general, is via G protein receptor kinases (GRK). Therefore, we hypothesize that age-related changes in GRKs are causative to this etiology in rat aorta. Herein, we investigate the activity and cellular distribution (cytoplasmic vs. membrane) of several GRK isoforms and beta-arrestin proteins. GRK activity was assessed in extracts from aortic tissue of 6-wk, 6-mo, 12-mo, and 24-mo-old male Fischer-344 rats using a rhodopsin phosphorylation assay. We also performed immunoblots on lysates from aorta with specific antibodies to GRK-2, -3, -5, and beta-arrestin-1. Results show an age-related increase in GRK activity. Furthermore, expression of GRK-2 (cytoplasmic and membrane), GRK-3 (cytoplasmic and membrane), and beta-arrestin (soluble) increased with advancing age, whereas GRK-5 (membrane) expression remained unchanged. These results suggest that age is associated with increased activity and expression of specific GRKs. This increase likely results in enhanced phosphorylation and desensitization of beta-ARs. These biochemical changes are consistent with observed aging physiology.

Angiotensin II enhances beta-adrenergic receptor-mediated vasorelaxation in aortas from young but not old rats

beta-Adrenergic receptor (beta-AR)-mediated (cAMP-dependent) vasorelaxation declines with advancing age. It has been shown that angiotensin II (ANG II), a potent vasoconstrictor, enhances cAMP-mediated vasorelaxation. Therefore, we questioned whether ANG II could reverse age-related, impaired beta-AR-mediated vasorelaxation and cAMP production. Pretreatment of aortic rings from 6-wk-old or 6-mo-old male Fischer 344 rats with ANG II significantly enhanced vasorelaxation induced by isoproterenol (Iso), a beta-AR agonist, and forskolin, a direct activator of adenylyl cyclase, but not dibutyryl-cAMP or isobutylmethylxanthine. The ANG II effect was blocked by losartan but not PD-123319 and was not observed in the aortas from 12- and 24-mo-old animals. Iso-stimulated cAMP production in the aorta was enhanced in the presence of ANG II in the 6-wk-old and 6-mo-old age groups only. Results suggest ANG II cannot reverse the age-related impairment in beta-AR-dependent vasorelaxation. We conclude aging may affect a factor common to both ANG II-receptors and beta-AR signaling pathways or aging may impair cross-talk between these two receptor pathways.

Viral-mediated gene delivery of constitutively activated G alpha s alters vasoreactivity

1. Decline in beta-adrenoceptor (beta-AR)-mediated function occurs with increasing age, as well as in multiple disease conditions. The mechanisms responsible for this decline include alterations in beta-AR itself, beta-AR coupling proteins, such as G-proteins, or other beta-AR-linked proteins, such as G-protein receptor kinases and/or phosphatases. 2. The present study examines the physiological effects of in vitro transfer of constitutively activated G alpha s (G alpha s-Q227L) to both cultured vascular smooth muscle cells (VSMC) and whole aortic tissue of 6-month-old (adult) animals via a replication-deficient Herpes simplex virus (HSV) vector. These studies were conducted to provide a model for future examination of the role of G alpha s in the age-related decline in beta-AR-mediated vasorelaxation. 3. Gene transfer was confirmed by western blotting for specific proteins. Aortic tissue infected with HSV-G alpha s-Q227L had reduced phenylephrine-induced contraction and enhanced isoproterenol-stimulated vasorelaxation. Infection of cultured VSMC with HSV-G alpha s-Q227L increased both basal- and isoproterenol-stimulated cAMP accumulation, whereas forskolin-stimulated cAMP production was unchanged. 4. These results implicate G alpha s as a target for further investigation in age-related changes in vascular reactivity and support the use of viral-mediated gene transfer as an effective tool to study adrenergic signal transduction and physiology in vascular tissue.

Impaired cholera toxin relaxation with age in rat aorta

Beta-adrenergic-mediated vasorelaxation declines with maturation and aging. Available data suggest that impaired stimulatory G-protein function could explain this deficit. We have previously found a loss of cholera toxin (CT)-stimulated adenosine diphosphate (ADP) ribosylation with age in rat aortic membrane preparations, without evidence for loss of the stimulatory alpha subunit of G protein (Gsalpha) by immunoblotting. The purpose of this investigation was to determine if cholera toxin-mediated vasorelaxation was also impaired with age. Aortic ring segments from 6 weeks, 6 months, 12 months, and 24 months old male F-344 rats were used. Contraction to KCl and phenylephrine was assessed along with relaxation to cholera toxin (azide-free), isoproterenol and forskolin. There were no age-related changes to KCl or phenylephrine contraction. There was a significant decrease with age in relaxation to isoproterenol. This loss with age was significantly greater with KCl-preconstricted vessels than phenylephrine-preconstricted vessels. There were no age-related changes in the relaxation to forskolin. There was a significant decrease with age in the maximal relaxation to cholera toxin as well as a rightward shift in the dose-response curve. Cholera toxin-stimulated adenosine 3', 5'-cyclic phosphate (cAMP) levels were measured and there was no increase in cAMP levels surrounding the time period associated with relaxation induced by cholera toxin. These data suggest that different preconstricting agents markedly affect the age-related changes in beta-adrenergic-mediated vasorelaxation. Furthermore, they suggest that the mechanism of cholera toxin-mediated vasorelaxation may not be mediated through increases in cAMP concentration.

Age-related changes in adenylyl cyclase activity in rat aorta membranes

Blood vessels from aged animals and humans have impaired relaxation and cAMP production to beta-adrenergic stimulation. Direct activators of adenylyl cyclase (AC) such as forskolin are not affected. We hypothesized that analogous findings would occur in membrane preparations. Aortic media membrane preparations from Fischer 344 rats of four age groups (6 weeks to 24 months) were studied. Basal AC activity increased significantly with age. Forskolin-stimulated activity compared to basal tended to be greater in the 6-week and 6-month preparations compared to the 12- and 24-month preparations. AC activity was assessed in the presence of the G protein activators (GTP, GppNHp, NaF). There was no age-related decrease in responsiveness. The receptor agonists isoproterenol (beta-adrenergic), and PGE-1 (prostaglandin), were studied. There was no significant age-related change in responsiveness over basal activity to either of these agonists. There was a slight, but significant increase in the isoproterenol responsiveness over GTP responsiveness in the 6-week-old animals which also approached significance in the 6-month-old animals, but was not seen in the 12- and 24-month-old animals. These data suggest that using a membrane system to assess age-related changes in beta-adrenergic responsiveness in vascular smooth muscle does not retain the robust differences seen in whole vessels.

Age-related changes in G proteins in rat aorta

Blood vessels from aged animals and humans have impaired relaxation to beta-adrenergic stimulation. We hypothesized that a loss of stimulatory G protein (Gs) or an increase in inhibitory G proteins (Gi) could explain this impairment. Aortic membranes from Fischer 344 rats of 4 age groups (6 week to 24 month) were studied. G-protein levels were initially assessed using cholera and pertussis toxin labeling. There was a marked decline in cholera toxin labeling (which primarily labels Gs alpha) from 6 weeks to 6 months which persisted in 12-month and 24-month animals. Pertussis toxin labeling (which primarily labels Gi alpha) showed only a slight decline with age. Western blotting was performed using specific antibodies for the alpha subunit of Gs, Gi1&2, Gi3, and G beta. There was no significant change in Gs alpha, Gi alpha, or G beta protein levels with age. We conclude there is a loss of cholera toxin-catalyzed ADP ribosylation with age, which does not represent a loss of the stimulatory alpha subunit of G protein. These data suggest that the loss of cholera toxin labeling seen with age may be a marker for loss of Gs alpha function.

The mouse creatine kinase paired E-box element confers muscle-specific expression to a heterologous promoter

E-box elements, with the CANNTG sequence motif, occur in numerous promoters and enhancers. We evaluated the tissue-specific expression properties of the paired murine E-box element from the mouse muscle creatine kinase (MCK) enhancer in a minimal heterologous promoter construct. A 46-bp fragment containing the paired E-box element in its wild-type (wt) configuration conferred high levels of muscle-specific expression in transfected embryonic chicken cell cultures. The expression from this paired E-box element was similar to that of the simian virus 40 (SV40) promoter/enhancer, but a 21-bp fragment containing a single E-box was inactive. We conclude that the paired E-box element from the MCK enhancer is sufficient for high levels of muscle-specific expression when placed upstream from a non-muscle TATA element.

Functional antagonism between YY1 and the serum response factor

The rapid, transient induction of the c-fos proto-oncogene by serum growth factors is mediated by the serum response element (SRE). The SRE shares homology with the muscle regulatory element (MRE) of the skeletal alpha-actin promoter. It is not known how these elements respond to proliferative and cell-type-specific signals, but the response appears to involve the binding of the serum response factor (SRF) and other proteins. Here, we report that YY1, a multifunctional transcription factor, binds to SRE and MRE sequences in vitro. The methylation interference footprint of YY1 overlaps with that of the SRF, and YY1 competes with the SRF for binding to these DNA elements. Overexpression of YY1 repressed serum-inducible and basal expression from the c-fos promoter and repressed basal expression from the skeletal alpha-actin promoter. YY1 also repressed expression from the individual SRE and MRE sequences upstream from a TATA element. Unlike that of YY1, SRF overexpression alone did not influence the transcriptional activity of the target sequence, but SRF overexpression could reverse YY1-mediated trans repression. These data suggest that YY1 and the SRF have antagonistic functions in vivo.

Influence of animal age on the beta-adrenergic system in cultured rat aortic and mesenteric artery smooth muscle cells

It has previously been reported that aortic smooth muscle cells cultured from old rats have a marked decline in beta-adrenergic stimulated cAMP accumulation. We wished to confirm this observation and determine whether this decline was secondary to loss of beta-adrenergic receptors (BAR). Primary cultures of aortic and mesenteric artery smooth muscle cells were obtained by enzymatic digestion from young and old male Fischer 344 rats. In aortic cells from old animals, there was a decline in beta-adrenergic receptor density and a rightward shift in the dose response curve to isoproterenol without a change in maximal cAMP accumulation. In mesenteric artery cells, there were no age changes in these parameters. Beta-adrenergic receptor subtype distribution was determined and was similar between all age groups and vessel types. These findings differ from whole tissue studies and suggest that cultured smooth muscle cells have limitations as a model for the aging adrenergic system.

Effect of age and hypoxia on beta-adrenergic receptors in rat heart

Previous reports suggest that hypoxia downregulates cardiac beta-adrenergic receptors from young rats. Because aging alters response to stress, we hypothesized an age-related alteration in the response to hypoxia. Male Fischer-344 rats, aged 3 and 20 mo, were divided into control and hypoxic groups. The hypoxic rats were exposed to hypobaric hypoxia (0.5 atm) for 3 wk. After hypoxic exposure, body weight decreased, hematocrit increased, right ventricular weight increased, and left ventricular weight decreased in all animals. beta-Adrenergic receptor density declined after hypoxic exposure in the young but not in the older animals, a change that was confined to the left ventricle. beta-Adrenergic receptor density in the right ventricle was significantly lower in the older animals than in the young animals. Plasma catecholamines (norepinephrine, epinephrine) drawn after the animals were killed (stress levels) decreased in young rats and increased in old rats after the exposure to hypoxia. Hypoxia is a useful physiological stress that elucidates age-related changes in cardiac beta-adrenergic receptor and catecholamine regulation that have not previously been described.

Chronic hypoxia increases beta-adrenergic receptor density in the lungs of young and old rats

To test the hypothesis that the ability to regulate beta-adrenergic receptor (BAR) density in response to chronic hypoxic stress is impaired by aging, we measured BAR density in the lungs of young (age 3 months) and aged (age 20 months) rats exposed to hypobaric hypoxia (1/2 atm) for 3 weeks. BAR density increased by 63% in the lungs of both young and aged rats exposed to chronic hypoxia. Lung BAR density was unaffected by aging, independent of hypoxic conditions. We conclude that the ability to respond to chronic hypoxic stress with increased lung BAR density is unaffected by aging in rats.

Beta-adrenergic function in aging. Basic mechanisms and clinical implications

Catecholamines have an important endocrine and neuroendocrine role in mediating a variety of autonomic functions. One consequence of normal aging, in particular in the cardiovascular system, is a decline in beta-adrenergic function associated with an alteration in responsiveness to beta-adrenergic therapy. The intrinsic ability for muscle contractility or relaxation is maintained with age and there appears to be an alteration in the process linking the receptor with the contractile or relaxation mechanisms. In rats, beta-adrenergic receptor density decreases with age in adipose tissues and most brain areas, is unchanged in lymphocytes, heart and lung, and increases in the liver. In humans, there are no receptor changes with age in either lymphocytes or brain. In contrast, the number of high-affinity receptors (or coupled receptors) decreases with age in most tissues. In addition, there is a decrease in membrane adenylate cyclase activity or cellular production of cyclic adenosine monophosphate (adenosine 3',5'-cyclic phosphate; cAMP). Plasma noradrenaline (norepinephrine) concentration increases with age. The reduced receptor number in some tissues (down-regulation), the reduced high-affinity receptors and the reduced hormone-stimulated adenylate cyclase activity with age suggests receptor desensitisation to increased plasma noradrenaline concentration. The inability of older animals to desensitise to beta-adrenergic agonists further supports this hypothesis. However, there is an additional post-receptor reduction in catalytic unit activity with age independent of desensitisation. Medications directed at the beta-adrenergic system are commonly used in the elderly. Many of the data on the impact of age on clinical responses are conflicting or unavailable. Concomitant disease, functional status, nutritional state and polypharmacy may play an even greater role than age. However, the available data can be used to guide the selection of therapy, anticipate side effects, and predict potential interactions with other medications and diseases.

Hyperadrenergic orthostatic intolerance as a result of postpartum blood loss

This article describes a young women in whom orthostatic intolerance developed as a result of protracted postpartum vaginal bleeding. The cardiovascular abnormalities were unresponsive to usual treatment measures, and she required combination therapy directed at increasing plasma volume and decreasing sympathetic nervous system activity. After resolution of her symptoms, the patient required no long-term therapy. Chronic blood loss has not been reported as a cause of this syndrome.

Diminished adrenal steroidogenic activity in aging rats: new evidence from adrenal cells cultured from young and aged normal and hypoxic animals

Adrenal cells from 2-6-month-old young rats (Y cells) and from 19-25-month-old aged male rats (O cells) were adapted to primary monolayer culture. The cultures of Y and O cells appeared to be primarily epithelial and rounded up in response to stimulation with adrenocorticotropic hormone (ACTH). The general morphology of O cells was comparable to that observed in Y cells except for the presence of lipofuscin-like granules, a cellular marker of aging, in O cells, but not in Y cells. ACTH-stimulated steroid production by O cells was 52% lower than that by Y cells. Exposure of intact young rats to hypoxia (0.5 atmosphere) for 21 days prior to sacrifice and culture resulted in a 122% increase of ACTH-stimulated adrenal steroidogenic activity in the cultured cells, but this effect was not observed in adrenal cells cultured from hypoxic aged rats. The results suggest that there is an age-related diminution in rat adrenal steroidogenic capacity in response to ACTH stimulation in culture derived from Y and O animals; hypoxic stress magnifies this difference.

Effects of meals and time of day on postural blood pressure responses in young and elderly subjects

Previous data suggest that postural and postprandial hypotension are common in elderly subjects. This study evaluated the effect of age, meals, and time of day on supine and standing blood pressure (BP) and heart rate in healthy young and elderly subjects. A postural BP protocol was performed on 10 young and 16 elderly subjects during an overnight stay. The protocol included first morning and postprandial readings. The systolic and diastolic BP responses to standing were not significantly different between the two groups and were not affected by time of day. Postprandial recumbent BPs declined significantly only in the older subjects. There was no effect of meals on the BP response to standing. We conclude that healthy elderly subjects have a postprandial decline in BP even when supine. However, the BP response to standing is similar in young and elderly subjects and is not impaired by overnight rest or meals. This suggests that the regulation of BP after meals and with standing may be different.

Orthostatic hypotension

Orthostatic hypotension is a rare finding in healthy elderly subjects, but is a common clinical problem in older patients. Assessment of symptoms and the blood pressure response to standing is an important part of the initial evaluation and follow-up of geriatric patients. Generally, more than one cause will be identified, and these patients respond to simple treatment measures. Identification and treatment of this disorder will improve function and independence in this population.

Effect of age on acute regulation of beta-adrenergic responses in mononuclear leukocytes

We studied the acute regulation of beta-adrenergic receptors and cAMP production in mononuclear leukocytes from young and old human subjects. After one hour of supine rest, healthy young and elderly subjects had similar beta-adrenergic receptor density and cAMP responses to isoproterenol. After 10 min of standing, beta-adrenergic receptor density and cAMP response increased in the young subjects. Elderly subjects had a similar increase in cAMP responses after standing, but no change in beta-adrenergic receptor density. Lymphocyte subsets and percent monocytes were not altered by age or posture, suggesting that this was not an artifact of changes in cell populations. Incubation in vitro of cells from both groups with catecholamines, at concentrations comparable to those achieved in plasma after standing, resulted in enhanced isoproterenol-mediated cAMP responses, but no change in beta-adrenergic receptor density. These data suggest that acute regulation of adrenergic signaling is affected by age, mediated in part by catecholamines, and may be relevant in the study of acute cardiovascular regulation.

Effect of timing and number of baseline blood pressure determinations on postural blood pressure response

We hypothesized that the blood pressure response to standing may depend on the method of establishing baseline blood pressure. Three hundred elderly subjects previously completed a postural blood pressure protocol with three supine baseline blood pressure readings obtained two minutes apart prior to standing. Comparison of the readings showed a significant drop between the first and the second (P less than .001) but not between the second and third supine systolic blood pressures. The difference between the first supine systolic blood pressure and the one minute standing blood pressure was significantly greater than that between the third supine systolic blood pressure and the one minute standing blood pressure (P less than .001). A second group was prospectively studied to determine whether the change in blood pressure after standing was greater if only a single baseline reading was taken rather than multiple readings, and whether the decline in blood pressure over three readings was related to duration supine or to the number of blood pressures taken. This group also demonstrated a decline in systolic blood pressure with three serial readings. We conclude that supine blood pressure declines significantly between the first and second readings taken two minutes apart and is secondary to the repetition of readings and not the duration supine. However, this change in supine blood pressure does not significantly alter the blood pressure response to standing. Thus, it appears that a single baseline supine blood pressure measurement is adequate for determining the postural blood pressure response, and that pooling of multiple baseline readings may not be appropriate.

Aging and postural hypotension. An update

Postural hypotension is a common clinical problem in elderly patients. Reported studies have investigated the epidemiology and mechanisms of this disorder. However, many of these data are based on subjects with diseases and medications also known to cause this disorder, which confuses the relative contributions of normal aging, disease, and medication effects. This review critically evaluates published studies on measurement, epidemiology, and mechanisms of postural hypotension in screened and unscreened elderly populations. Pertinent age-related changes in physiology and the relationship of postural hypotension in the elderly to other models of postural hypotension are reviewed. Areas of current and future research are outlined.

Effect of age and posture on human lymphocyte adenylate cyclase activity

1. A number of age-related changes have been reported in the catecholamine-adrenoceptor-adenylate cyclase system. Most of the data available on these alterations come from resting subjects; the response to acute stress may provide additional insights into the age effect on these responses. 2. We measured supine and 10 min upright plasma noradrenaline and lymphocyte adenylate cyclase activity in ten healthy elderly subjects (age 66-80 years) and seven healthy young subjects (age 27-34 years). 3. Isoprenaline stimulation of lymphocyte adenylate cyclase activity was not significantly different between supine and upright positions or between elderly and young subjects. There was a marked increase in forskolin-stimulated adenylate cyclase activity in the upright posture in both elderly and young subjects. The increment over supine levels was 70% in the elderly (P less than 0.025) and 73% in the young (P less than 0.05). This enhanced forskolin activity was not seen in two young subjects who became syncopal. 4. These data suggest that enhanced forskolin-stimulated adenylate cyclase activity occurs after 10 min of upright posture in both elderly and young subjects, and may be relevant to immediate blood pressure regulation. We were unable to demonstrate any age-related differences in these acute adrenergic responses.

Low prevalence of postural hypotension among community-dwelling elderly

Postural hypotension (PH) has a prevalence of about 20% in most large studies of elderly individuals; however, these studies do not exclude subjects with diseases and medications known to cause PH. We sought to determine the prevalence of PH in healthy, community-living, elderly individuals in contrast to those with known risk factors for the condition. We measured supine and one-minute standing blood pressures in 300 independently living elderly persons who visited a senior citizen health screening program. Subjects were divided into two groups: those with known risk factors (n = 175) and those without (n = 125). The prevalence of PH (systolic decrease, greater than or equal to 20 mm Hg) for for the entire population was 10.7%. In the group with risk factors, the prevalence was 13.7% (24/175), compared with 6.4% in the group without risk factors (8/125). Supine hypertension was associated with PH, but there was no relationship between the presence of PH and age, history of falls, symptoms on standing, or recent meal. These data suggest that PH is a relatively uncommon finding in healthy elderly, its prevalence is significantly related to risk factors, and its association with falls or symptoms may be less than previously reported.

Orthostatic hypotension due to hypertrophic cardiomyopathy and autonomic failure

A case of orthostatic hypotension due to the combination of hypertrophic obstructive cardiomyopathy and autonomic failure is described. The interacting pathophysiologic features of the two disorders and response to therapy are discussed. The value of dynamic cardiac auscultation and Doppler echocardiography in patients with postural blood pressure changes is demonstrated.

Successful thrombolytic therapy in two patients with renal vein thrombosis

Thrombolytic therapy was administered to two patients with angiographically documented renal vein thrombosis. One patient with bilateral thrombotic disease complicating membranous glomerulonephritis was treated with systemic streptokinase; the second patient had unilateral renal vein thrombosis associated with chronic pyelonephritis and was treated with streptokinase and urokinase administered directly into the involved vessel. Lysis of all thrombus material was demonstrated by follow-up renal venography and was associated with a gratifying improvement of clinical well-being and laboratory function. These cases demonstrate the feasibility of dissolving renal vein thrombi of presumed recent onset and suggest that rapid lysis of the thrombus accelerates functional and clinical recovery.