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Logo of biosexdiffBioMed CentralBiomed Central Web Sitesearchsubmit a manuscriptregisterthis articleBiology of Sex DifferencesJournal Front Page
 
Biol Sex Differ. 2012; 3: 1.
Published online Jan 3, 2012. doi:  10.1186/2042-6410-3-1
PMCID: PMC3264497
Alterations in vasomotor systems and mechanics of resistance-sized mesenteric arteries from SHR and WKY male rats following in vivo testosterone manipulation
Jonathan D Toot,1 John J Reho,1,2 Rolando J Ramirez,1,2 Jacqueline Novak,3 and Daniel L Elycorresponding author1,2
1Department of Biology, 303 Carroll St.,The University of Akron, Akron, OH 44325-3908
2Program in Integrated Biosciences, 303 Carroll St.,The University of Akron, Akron, OH 44325-3908
3Department of Mathematics and Science,2020 E Maple St. Walsh University, North Canton, OH 44720-3336
corresponding authorCorresponding author.
Jonathan D Toot: jtoot/at/hotmail.com; John J Reho: jjr13/at/zips.uakron.edu; Rolando J Ramirez: rjr/at/uakron.edu; Jacqueline Novak: jnovak/at/walsh.edu; Daniel L Ely: ely1/at/uakron.edu
Received August 26, 2011; Accepted January 3, 2012.
Abstract
Background
Testosterone (T) and the sympathetic nervous system each contribute to the pathology of hypertension. Altered blood vessel reactivity is also associated with the pathology of high blood pressure. The purpose of this study was to examine the effects of T manipulation in the regulation of resistance-sized blood vessel reactivity.
Methods
Adult spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) male rats at 8 weeks of age were used. The rats were divided into groups consisting of gonadally intact controls (CONT), castrate with sham implant (CAST) and castrate with T implant (CAST + T) (n = 6 to 12 per group). Following a short-term period of T treatment (approximately 4 weeks), plasma norepinephrine (NE) and plasma T were assessed by performing high-performance liquid chromatography and RIA, respectively. Resistance-sized mesenteric artery reactivity was assessed on a pressurized arteriograph for myogenic reactivity (MYO), phenylephrine (PE) responsiveness and passive structural mechanics.
Results
SHR and WKY males exhibited similar physiological trends in T manipulation, with castration significantly lowering plasma T and NE and T replacement significantly increasing plasma T and NE. T manipulation in general resulted in significant alterations in MYO of second-order mesenteric arteries, with T replacement decreasing MYO in SHR (P < 0.05) compared to CONT, T replacement increasing MYO, and CAST decreasing MYO in WKY rats (P < 0.001) compared to CONT rats. Additionally, PE-induced constriction was significantly altered in both strains following T treatment, with the effective concentration of PE to constrict the vessel to 50% of the total diameter significantly increased in the CAST + T SHR compared to CONT (P < 0.05). Comparisons of passive structural mechanics between SHR and WKY treatment groups indicated in SHR a significantly increased wall-to-lumen ratio and decreased circumferential wall stress compared to WKY treatment groups.
Conclusions
These data suggest that T and NE are involved in a complex interaction with both myogenic reactivity and structural alterations of resistance-sized blood vessels and that these factors likely contribute to the development and maintenance of hypertension.
Keywords: testosterone, norepinephrine, blood vessel, myogenic
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