Chronic exposure of rats to cold (5-6 degree C.) induces hypertension, which is characterized by an increase in systolic, diastolic, and mean blood pressures, as well as cardiac (left ventricular) hypertrophy. This is an important finding since it represents for the first time a """"""""naturally occurring"""""""" hypertension which is induced without surgical intervention; administration of excessive doses of hormones or drugs, or generic manipulation. The overall objective of this proposal is to assess potential mechanisms that may contribute to the development of cold-induced hypertension. One possibility relates to the fact that cold-treated rats ingest excessive amounts of NaC1 as a result of an obligatory increase in food intake.
The aim of the first experiment is to investigate this possibility. A further possibility relates to the mediation of the renin-angiotensin-aldosterone (RAA) system in the induction of hypertension during exposure to cold. It is postulated that increased activity of the RAA system, coupled with ingestion of excessive amounts of NaC1, result in the induction of a mineralocorticoid-type of hypertension. Therefore, the aim of an additional experiment is to test the effect of chronic blockade of the angiotensin I converting enzyme by captopril on the development of cold-induced hypertension, as well as its rate of return to control level after removal from cold. A further aim is to assess changes that may occur in various components of the RAA system during chronic exposure to cold, including plasma renin activity, plasma aldosterone and renin contractions mRNA for renin substrate in several tissues, vascular responsiveness to exogenous administration of angiotensin II, and the regulation of receptors for angiotensin II and the regulation of receptors for angiotensin II in brain and other tissues. In addition, it is the aim of a further study to assess whether a change in baroreceptor function precedes, or results from, the development of hypertension during exposure to cold. Changes in the regulation of alpha1 - and alpha2 -adrenoceptors in the brain will also be assessed during exposure to cold because of their potential involvement in the development of hypertension. Finally, the possibility that intermittent exposure to cold can induce hypertension will be tested.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL039154-07
Application #
2219201
Study Section
Metabolic Pathology Study Section (MEP)
Project Start
1987-07-01
Project End
1995-06-30
Budget Start
1993-07-01
Budget End
1995-06-30
Support Year
7
Fiscal Year
1993
Total Cost
Indirect Cost
Name
University of Florida
Department
Physiology
Type
Schools of Medicine
DUNS #
073130411
City
Gainesville
State
FL
Country
United States
Zip Code
32611
Peng, JianFeng; Kimura, Birgitta; Phillips, M Ian (2002) The predominant role of brain angiotensinogen and angiotensin in environmentally induced hypertension. Regul Pept 110:25-32
Peng, J F; Phillips, M I (2001) Opposite regulation of brain angiotensin type 1 and type 2 receptors in cold-induced hypertension. Regul Pept 97:91-102
Peng, J F; Kimura, B; Fregly, M J et al. (1998) Reduction of cold-induced hypertension by antisense oligodeoxynucleotides to angiotensinogen mRNA and AT1-receptor mRNA in brain and blood. Hypertension 31:1317-23
Sun, Z; Fregly, M J; Rowland, N E et al. (1996) Comparison of changes in blood pressure and dipsogenic responsiveness to angiotensin II in male and female rats chronically exposed to cold. Physiol Behav 60:1543-9
Fregly, M J; Shechtman, O; Rowland, N E (1995) Increased dipsogenic responsiveness to angiotensin II in rats exposed to cold: rate of loss after return to thermoneutral ambient temperature. Proc Soc Exp Biol Med 209:54-9
Fregly, M J; Cade, J R (1995) Effect of pyridoxine and tryptophan, alone and combined, on the development of deoxycorticosterone acetate-induced hypertension in rats. Pharmacology 50:298-306
Fregly, M J; Rowland, N E (1995) Effect of administration of angiotensin II and isoproterenol, alone and in combination, on drinking and tail skin temperature of the rat. Pharmacol Biochem Behav 51:83-8
Sun, Z; Fregly, M J; Cade, J R (1995) Effect of renal denervation on elevation of blood pressure in cold-exposed rats. Can J Physiol Pharmacol 73:72-8
Fregly, M J; Schechtman, O (1994) Direct blood pressure measurements in rats during abrupt exposure to, and removal from, cold air. Proc Soc Exp Biol Med 205:119-23
Fregly, M J; Rossi, F; Sun, Z et al. (1994) Effect of chronic treatment with prazosin and L-arginine on the elevation of blood pressure during cold exposure. Pharmacology 49:351-62

Showing the most recent 10 out of 31 publications