Dept. of Physiology and Biophysics, Institute of Biomedical Sciences, University of Sao Paulo, Av. Prof. Lineu Prestes, 1524, 05508-900 São Paulo, SP, Brazil.
Don’t judge too harshly—this is my first time!
This journal article was brought to my attention by Nick -- since it included my favorite enzyme Tyrosine Hydroxylase! In this article the researchers are trying to quantify the amount of sympathetic activity in different tissues simultaneously. In this study they examine the kidney, heart and skeletal muscle. Jut to reiterate, tyrosine hydroxylase, is one of the enzymes in the chain that converts the amino acid tyrosine to norepinephrine— which is one of the main neurotransmitters that causes vasoconstriction as part of the sympathetic response. In this study both WKY and SHR rats were used.
Burgi et al., propose that simultaneous measurement of THir (tyrosine hydroxylase immunoreactivity—which is what Nick does in our lab) in different vascular beds can be used to determine SNA activity in SHR rats as an indication of hypertension. They then compared their findings to normotensive rats for control.
Interestingly out of the three vascular tissue beds examined (kidney, heart and skeletal muscle), they found higher THir in the kidney and heart tissues of the SHR, however in the skeletal muscle THir was not higher between the SHR and WKY groups. There are many reasons outlined in the discussion as to why this might be the case. The authors also showed in their results that differential sympathetic activity was shown by taking nerve recordings from the renal (RSNA) and lumbar (LSNA). They showed that there was increased RSNA in the SHR and unchanged LSNA activity which coincided with the results of increased THir in the kidney and heart, and lower THir in the skeletal muscles as compared to WKY.
The main point of this paper set out to prove that THir can be used as an indicator for sympathetic activity in different tissues simultaneously.
Nice job Suzan. I haven't read the paper yet but was wondering if they quoted Andrew Allen's data that demonstrates elevated LSNA in the SHR. It would interesting to hear how they resolve the difference. Pat
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