The Sry3 Y chromosome locus elevates blood pressure and renin-angiotensin system indexes.

BACKGROUND: Sex-determining region Y (Sry) is a transcription factor. Our research group has shown that there are multiple copies of Sry in Wistar-Kyoto (WKY) and spontaneous hypertensive (SHR) rats, and that they have novel functions separate from testes determination. OBJECTIVE: We hypothesized that exogenously delivered Sry3 to the normotensive WKY male kidney would activate the renin-angiotensin system (RAS) and raise blood pressure (BP), based on previous in vitro studies. METHODS: Sry3 or control vector was electroporated to the left kidney of male WKY rats and the following measurements were taken: BP by telemetry, renin-angiotensin measures by radioimmunoassay, plasma and tissue catecholamines by HPLC with electrochemical detection, sodium by flame photometry, and inulin by ELISA. RESULTS: Sry3 increased BP 10 to 20 mm Hg compared with controls (P < 0.01) and produced a significant 40% decrease in urine sodium compared with controls (P < 0.05). Sry3 increased renal angiotensin II and plasma renin activity by >100% compared with controls (P < 0.01 and P < 0.05, respectively). CONCLUSION: The findings presented here confirm and extend the argument for Sry3 as one of the genes responsible for the SHR hypertensive Y chromosome phenotype and are consistent with increased tissue RAS activity due to Sry3 and increased sodium reabsorption.

Testosterone increases myogenic reactivity of second-order mesenteric arteries in both defective and normal androgen receptor adult male rats.

BACKGROUND: Testosterone (T) and the androgen receptor (AR) are involved in mechanisms associated with hypertension and vessel reactivity. OBJECTIVE: To investigate T and the AR on blood vessel reactivity, testicular feminized male (TFM; AR deficient males) and normal androgen receptor (NAR) male rats were used. Therefore, if the functional AR is necessary for plasma T to regulate vessel responsiveness, TFM males will exhibit altered vessel function compared to NAR males. METHODS: Adult (16 weeks of age) TFM or NAR males were assigned to the following treatment groups: gonadal intact controls (CONT), castrate (CAST), or castrate with T replacement (CAST+T) with (n=8-10/group). RESULTS: Plasma T followed a consistent pattern with CAST+T elevated compared to CONT and CAST TFM and NAR males. In addition, CAST plasma T was significantly decreased compared to CONT and CAST+T in TFM and NAR males. In a similar manner for systolic blood pressure (SBP), CAST lowered SBP compared to CONT in both NAR and TFM. Following 8 weeks of treatment, second-order mesenteric artery responses to changes in intraluminal pressure (myogenic reactivity) were analyzed using a pressure arteriograph system. Both TFM (P < 0.05) and NAR (P < 0.05) CAST groups revealed a decrease in myogenic reactivity compared to CONT. Following T treatment the TFM CAST+T myogenic reactivity returned to CONT levels, whereas the NAR CAST+T myogenic reactivity increased a further 10%. CONCLUSION: The results of this study indicate that T differentially regulates mesenteric artery reactivity in TFM and NAR males. Our data also demonstrate that both AR and/or non-AR mediated mechanisms may partially contribute to SBP regulation.

Colony social stress differentially alters blood pressure and resistance-sized mesenteric artery reactivity in SHR/y and WKY male rats.

Increased sympathetic nervous system (SNS) activity, testosterone, and spontaneously hypertensive rat Y chromosome (SHR Yc) play a role in a genetic model of hypertension. Male rats with the SHR Yc and Wistar-Kyoto (WKY) autosomes (denoted SHR/y) exhibit these characteristics when compared to rats with the WKY Yc and WKY autosomes (denoted WKY). We hypothesized that chronic social stress will increase blood pressure and SNS activity more in SHR/y males compared to WKY males, resulting in increased myogenic reactivity along with decreased vasoconstriction of small mesenteric arteries. SHR/y and WKY males were housed in strain- specific colonies (10 males with 10 females) or as controls (10 males). Systolic blood pressure (SBP) and blood samples were collected prior to termination. Second-order mesenteric arteries were studied using a pressure arteriograph in which myogenic reactivity and phenylephrine (PE) responsiveness were measured. SHR/y colony SBP, and circulating norepinephrine and testosterone concentrations were elevated compared to control and WKY colony males (p < 0.05). Mesenteric artery myogenic reactivity was increased in SHR/y colony males (p < 0.001). Mesenteric arteries from SHR/y colony males exhibited a significant decrease in PE-induced constriction. Colony social stress elevated both SNS activity and testosterone level which may be responsible for the increased mesenteric artery myogenic reactivity, and SBP as noted in SHR/y males.

Review of the Y chromosome, Sry and hypertension.

The following review examines the role of the SHR Y chromosome and specifically the Sry gene complex in hypertension and potential mechanisms that involve the sympathetic nervous system and renin-angiotensin system. There are consistent gender differences in hypertension, with a greater proportion of males affected than females in most mammalian populations. Our earlier studies demonstrated that a portion of the gender differences in blood pressure (BP) in the SHR rat mapped to the SHR Y chromosome. In rats, males with the SHR Y chromosome have higher BP than females, or males with a different Y chromosome. Consistent with these results, several human population studies have confirmed a Y chromosome effect on BP. Our more recent studies focus on a transcription factor, Sry, as the locus involved in not only BP modulation but effects on other phenotypes. The Sry locus is an evolutionarily conserved locus on the mammalian Y chromosome responsible for testis determination and is a transcription factor. The Sry locus contains a highly conserved High Mobility Group (HMG) box region responsible for DNA binding. Mutations in the HMG box result in sex reversal. We have found multiple functional copies of Sry in SHR and WKY male rats. There is abundant evidence that testes determination may not be Sry's only function as it is expressed in the brain, kidney and adrenal gland of adult males. These findings have potential implications for gender physiology research which involves, the sympathetic nervous system, renin-angiotensin system, androgen receptor regulation and prostate physiology.

Delivery of sry1, but not sry2, to the kidney increases blood pressure and sns indices in normotensive wky rats.

BACKGROUND: Our laboratory has shown that a locus on the SHR Y chromosome increases blood pressure (BP) in the SHR rat and in WKY rats with the SHR Y chromosome (SHR/y rat). A candidate for this Y chromosome hypertension locus is Sry, a gene that encodes a transcription factor responsible for testes determination. The SHR Y chromosome has six divergent Sry loci. The following study examined if exogenous Sry1 or Sry2 delivered to the kidney would elevate renal tyrosine hydroxylase, renal catecholamines, plasma catecholamines and telemetered BP over a 28 day period. We delivered 50 mug of either the expression construct Sry1/pcDNA 3.1, Sry2/pcDNA 3.1, or control vector into the medulla of the left kidney of normotensive WKY rats by electroporation. Weekly air stress was performed to determine BP responsiveness. Separate groups of animals were tested for renal function and plasma hormone patterns and pharmacological intervention using alpha adrenergic receptor blockade. Pre-surgery baseline and weekly blood samples were taken from Sry1 electroporated and control vector males for plasma renin, aldosterone, and corticosterone. BP was measured by telemetry and tyrosine hydroxylase and catecholamines by HPLC with electrochemical detection. RESULTS: In the animals receiving the Sry1 plasmid there were significant increases after 21 days in resting plasma norepinephrine (NE, 27%) and renal tyrosine hydroxylase content (41%, p < .05) compared to controls. BP was higher in animals electroporated with Sry1 (143 mmHg, p < .05) compared to controls (125 mmHg) between 2-4 weeks. Also the pressor response to air stress was significantly elevated in males electroporated with Sry1 (41 mmHg) compared to controls (28 mmHg, p < .001). Sry2 did not elevate BP or SNS indices and further tests were not done. The hormone profiles for plasma renin, aldosterone, and corticosterone between electroporated Sry1 and control vector males showed no significant differences over the 28 day period. Alpha adrenergic receptor blockade prevented the air stress pressor response in both strains. Urinary dopamine significantly increased after 7 days post Sry electroporation. CONCLUSION: These results are consistent with a role for Sry1 in increasing BP by directly or indirectly activating renal sympathetic nervous system activity.

Testosterone influences renal electrolyte excretion in SHR/y and WKY males.

BACKGROUND: The Y-chromosome (Yc) and testosterone (T) increase blood pressure and may also influence renal electrolyte excretion. Therefore, the goal of this study was to determine if the Yc combined with T manipulation could influence renal Na and K excretion. METHODS: To investigate the role of the Yc and T, consomic borderline hypertensive (SHR/y) and normotensive Wistar-Kyoto (WKY) rat strains were used (15 weeks) in three T treatment groups: castrate, castrate with T implant and gonadally intact males. Urine was collected (24 hrs at 15 weeks of age) for Na and K measurements by flame photometry. RT-PCR was used to demonstrate the presence of renal androgen receptor (AR) transcripts. Plasma T and aldosterone were measured by RIA. In another experiment the androgen receptor was blocked using flutamide in the diet. RESULTS: Na and K excretion were decreased by T in SHR/y and WKY. AR transcripts were identified in SHR/y and WKY kidneys. Plasma aldosterone was decreased in the presence of T. Blockade of the AR resulted in a significant increase in Na excretion but not in K excretion in both SHR/y and WKY males. CONCLUSION: T influences electrolyte excretion through an androgen receptor dependent mechanism. There was not a differential Yc involvement in electrolyte excretion between WKY and SHR/y males.

Novel biostable and biocompatible amphiphilic membranes.

We determined the biostability and biocompatibility of two types of amphiphilic conetworks (APCNs): (1) hydrophilic poly(N,N-dimethyl acrylamide) (PDMAAm) and hydrophobic polydimethylsiloxane (PDMS) microdomains co-crosslinked with polymethylhydrosiloxane (PMHS) clusters (PDMAAm/PMHS/PDMS), and (2) poly(ethylene glycol) (PEG) and PDMS microdomains co-crosslinked with two specially designed small-molecule crosslinking agents SiC(6)H(5)(SiH)(2)OEt (Y) and polypentamethylhydrocyclosiloxane (PD(5)) (PEG/Y or PD(5)/PDMS). Negative standards for comparing biocompatibility and biostability were crosslinked PDMS. Biostability was assessed by quantitatively determining extractables, equilibrium water swelling, mechanical properties (stress-strain response) of polymer samples before and after implantation in rats for up to 8 weeks, and oxidative accelerated degradation test. Biocompatibility was assessed by determining body weight, fibrous tissue encapsulation, fluid accumulation, and by histological evaluation of lymphocyte infiltration, fibrous tissue accumulation and collagen deposition. According to these stringent metrics PDMAAm/PMHS/PDMS is both biostable and biocompatible, whereas PEG/Y or PD(5)/PDMS degrades in living tissue but is biocompatible. Surprisingly, the overall biocompatibility scores of these APCNs were superior to those of the PDMS negative standard.

Sry delivery to the adrenal medulla increases blood pressure and adrenal medullary tyrosine hydroxylase of normotensive WKY rats.

BACKGROUND: Our laboratory has shown that a locus on the SHR Y chromosome increases blood pressure (BP) in the SHR rat and in WKY rats that had the SHR Y chromosome locus crossed into their genome (SHR/y rat). A potential candidate for this Y chromosome hypertension locus is Sry, a gene that encodes a transcription factor that is responsible for testes development and the Sry protein may affect other target genes. METHODS: The following study examined if exogenous Sry would elevate adrenal Th, adrenal catecholamines, plasma catecholamines and blood pressure. We delivered 10 mug of either the expression construct, Sry1/pcDNA 3.1, or control vector into the adrenal medulla of WKY rats by electroporation. Blood pressure was measured by the tail cuff technique and Th and catecholamines by HPLC with electrochemical detection. RESULTS: In the animals receiving Sry there were significant increases after 3 weeks in resting plasma NE (57%) and adrenal Th content (49%) compared to vector controls. BP was 30 mmHg higher in Sry injected animals (160 mmHg, p < .05) compared to vector controls (130 mmHg) after 2-3 weeks. Histological analysis showed that the electroporation procedure did not produce morphological damage. CONCLUSION: These results provide continued support that Sry is a candidate gene for hypertension. Also, these results are consistent with a role for Sry in increasing BP by directly or indirectly activating sympathetic nervous system activity.

Regulation of tyrosine hydroxylase gene transcription by Sry.

Testes determining factor Sry is encoded by the Sry locus on the Y chromosome and may be involved in the regulation of blood pressure. Here we tested the hypothesis that Sry regulates transcription of tyrosine hydroxylase (TH), the rate-limiting enzyme in the biosynthesis of catecholamines. Sry was found to be expressed in catecholaminergic regions, in male but not female rats. Co-transfection of PC12 cells with expression vector for Sry and the reporter construct [p5'TH(-773/+27)/Luc], containing 773 of the proximal nucleotides of the TH promoter directing luciferase reporter activity, led to elevation of reporter activity. The reporter activity of a shorter construct [p5'TH(-272/+27)/Luc] lacking putative Sry sites also responded to Sry. However, mutation of the AP1 site in the TH promoter greatly reduced induction by Sry, indicating that the regulation is primarily at this motif. The remaining, significantly increased expression with the mutated TH promoter construct may reflect Sry function at other sites in addition to the AP1 motif. These results reveal that Sry can regulate TH transcription and suggest that this may be one of the mechanisms of Sry mediated regulation of catecholamine biosynthesis in catecholaminergic neurons in males.

The SHR Y-chromosome increases testosterone and aggression, but decreases serotonin as compared to the WKY Y-chromosome in the rat model.

The Spontaneously Hypertensive Rat (SHR) model was used to test the hypothesis that a locus on the SHR Y-chromosome is responsible for increased aggression resulting from increased serum testosterone and decreased amygdala serotonin content compared to the WKY Y-chromosome. To examine the Y-chromosome in SHR and WKY males, consomic Y-chromosome strains were used (WKY.SHR-Y and SHR.WKY-Y). Novel resident intruder tests and intra-colony scarring behavioral paradigms were used to measure aggression in a colony environment. Both resident intruder test attack number and wounding, along with intra-colony scarring scores showed the colony males with the SHR Y-chromosome (SHR and WKY.SHR-Y strains) were more aggressive than the colony males with the WKY Y-chromosome (WKY and SHR.WKY-Y strains). The SHR Y-chromosome colony male animals also had significantly higher serum testosterone, as well as overall lower amygdala serotonin content than the WKY Y-chromosome colony male animals. The results suggest that these behavioral and physiological differences between the SHR and WKY strains are a result of a mutation in the non-pseudoautosomal region unique to the Y-chromosome.

An examination of perceived stress in family caregivers of older adults with heart failure.

This investigation evaluates the moderating influence of social support on the negative effects of stress for family caregivers and validates the Perceived Stress Scale as a standard of measurement. Seventy-five family caregivers to older adults with heart failure were interviewed in their homes about perceived stress, depressive symptoms, and social support after hospital discharge. The Perceived Stress Scale demonstrated internal consistency. Social support did not moderate the effects of stress on depressive symptoms. Lack of a significant association between salivary cortisol and the Perceived Stress Scale did not support testing of construct validity. Stress levels, however, frequently vary due to caregiving demands and additional influencing factors.

Social stress increases blood pressure and cardiovascular pathology in a normotensive rat model.

Territorial stress (TS) elevates blood pressure (BP) in several mammalian species. However, cardiovascular pathology following chronic stress has not been consistently shown in a non-genetic hypertension model. Therefore, the hypothesis tested was that social stress would directly increase: BP, collagen deposition in coronary and mesenteric arteries, and myocardial fibrosis. Wistar-Kyoto (WKY) male rats, four weeks of age, were divided into one of three groups: controls (n = 9), territorial stress (TS, n = 12), and social isolation followed by territorial stress (SITS, n = 11). Blood pressure was measured biweekly, and blood samples biweekly for serum testosterone, corticosterone, epinephrine and norepinephrine. Blood pressure significantly increased in the TS (130 mmHg, p < 0.05) and SITS (150 mmHg, p < 0.05) groups, compared to controls (120 mmHg, ANOVA, F = 6.7, p < 0.001). Coronary collagen was increased 47% in the TS group and 90% in the SITS group compared to controls (p < 0.05). The coronary wall/lumen ratio increased significantly (45%, p < 0.05) in the SITS group compared to the controls. Myocardial fibrosis was increased 27% in the TS group and 74% in the SITS group compared to controls (p < 0.05). In conclusion, stress treatments increased BP and cardiac pathology in a normotensive rat strain.

Estradiol increases salt intake in female normotensive and hypertensive rats.

The objective of this study was to examine whether or not estradiol (E2) alters sodium intake in hypertensive and normotensive female rats. It was hypothesized that higher doses of E2 would increase sodium consumption and that this response would be greater in spontaneously hypertensive rats (SHR) compared with Wistar Kyoto (WKY) rats. The study involved female SHR and WKY (n = 12/group). All animals were ovariectomized. Six of twelve rats from each strain received three progressively larger doses of beta-estradiol propionate (each dose lasting 2 wk), whereas the other six rats from each strain received sham implants. Blood E2 levels were measured by radioimmunoassay after each 2-wk period, allowing a 10-day washout period before the next E2 dose. Rats had access to 0.0, 0.5, 1.0, and 1.5% NaCl solutions to drink throughout the experiment. There was a significant positive correlation between sodium intake and plasma E2 (r = 0.8, P < 0.001). Both strains avoided the 1.5% NaCl, and the increased sodium intake was achieved by an increase in consumption of the 0.5% NaCl. SHR females consumed more sodium than WKY females, which is similar to what has been observed in males of these strains. In conclusion, E2 was positively correlated with sodium intake in both strains of rat, with the hypertensive rats consuming more sodium than the normotensive rats.

Noradrenergic content and turnover rate in kidney and heart shows gender and strain differences.

The objective of this study was to compare strain and gender differences in kidney and heart norepinephrine (NE) content and turnover rate in normotensive Wistar-Kyoto rats (WKY) and spontaneously hypertensive rats (SHR, SHR/a, and SHR/y). Our laboratory has shown that the Y chromosome has a significant effect on blood pressure in the SHR model of hypertension through the use of two new rat stains, SHR/a and SHR/y, to study the Y chromosome. SHR/a have a SHR autosomal genetic background with a WKY Y chromosome, whereas the SHR/y rats have a WKY autosomal genetic background with a SHR Y chromosome. Tissues were homogenized after alpha-methyl-DL-p-tyrosine injection and analyzed for NE. The male kidney NE content was significantly lower in the WKY compared with the SHR, SHR/y, and SHR/a. Kidney and heart NE content was significantly higher in females compared with males in all strains except the SHR/y. The WKY and SHR/y females had significantly lower kidney NE turnover rates, and the SHR and SHR/a females had significantly higher kidney NE turnover rates than strain-matched males. This study suggests both a strain and gender difference in sympathetic nervous system activity through noradrenergic neurotransmission.