Diabetes mellitus in Brattleboro rats: cardiovascular, fluid, and electrolyte status

Abstract

Because plasma arginine vasopressin (AVP) levels are raised during streptozotocin (STZ)-induced diabetes mellitus (DM), it is possible that AVP contributes to the pattern of change in fluid and electrolyte handling and cardiovascular status after STZ treatment. Therefore we have made daily measurements of cardiovascular and metabolic variables in normal (Long-Evans) and AVP-deficient (Brattleboro) rats treated with saline or STZ. Twenty-four days after STZ, both strains had similar weight loss and increases in fluid intake, but the increase in food intake was greater in Long-Evans than in Brattleboro rats. After STZ, bradycardia developed in both strains, but only Brattleboro rats had reduced blood pressure. Plasma variables were measured 25 days after STZ. Packed cell volume and plasma sodium concentration were reduced in STZ-treated Long-Evans rats compared with saline-treated controls but were unchanged in STZ-treated Brattleboro rats. The results indicate that although AVP deficiency does not seriously affect the ability to maintain fluid and electrolyte balance after STZ treatment, there may be consequences for cardiovascular control.

The effects of endothelin‐1 and NG‐nitro‐l‐arginine methyl ester on regional haemodynamics in conscious rats with streptozotocin‐induced diabetes mellitus

“…Bradycardia following STZ treatment has been reported by several authors (e.g. Stuesse et al, 1982;Carbonell et al, 1987;Hebden et al, 1987a;Tomlinson et al, 1989;1990). Tomlinson et al (1990) have shown that Brattleboro (i.e.…”

“…Several studies have reported on resting arterial blood pressure following STZ treatment; some have shown diabetic rats are hypertensive (Kawashima et al, 1978;Bunag et al, 1982;Funakawa et al, 1983), whereas others have found they are normotensive (Rodgers, 1986;Yamamoto, 1988) or hypotensive (Kohler et al, 1980;Hebden et al, 1987a;Kusaka et al, 1987;Tomlinson et al, 1989;1990). The difference between the results from this present study and our earlier studies, in which we reported hypotension in diabetic rats (Hebden et al, 1987a,b;Tomlinson et al, 1989;1990), is that previously both systolic and diastolic blood pressures were recorded, and it was systolic pressure which was consistently reduced (Hebden et al, 1987a;Tomlinson et al, 1989). In the present work we also observed a reduction in systolic blood pressure following STZ treatment (data not shown), but we measured electronically-derived mean blood pressure (in order to calculate vascular conductances) and this was not reduced because in the bradycardic, STZ-treated rats the pressure wave form is broader than in control animals.…”

“…(Hebden et al, 1986;Tomlinson et al, 1989). Blood glucose levels were determined from a tail vein blood sample, 4 days after the STZ injection, by use of a Reflomat (Boehringer, Mannheim); those rats with blood glucose levels of greater than 12mmoll-were considered diabetic and were entered into the experiment.…”

Vasopressin contributes to hyperfiltration, albuminuria, and renal hypertrophy in diabetes mellitus: Study in vasopressin-deficient Brattleboro rats

“…In this study, focused mainly on cardiovascular function, glycemia in control LE rats was 7.3 mmol͞l. Glycosuria and renal function were not evaluated (32).…”

Vasopressin and Diabetes mellitus

“…On the other hand, a diminished contribution of vasopressin, possibly due to diminished pressor responsiveness, was suspected during blood pressure recovery following experimentally induced acute hypotension in rats [47]. Finally, when DM is induced in Brattleboro rats genetically lacking vasopressin, they exhibit a fall in blood pressure, a feature not observed in control rats in which vasopressin secretion can increase during DM [48]. If the vascular V1a receptors are not desensitized in DM, the permanent rise in the vasopressin level to which they are exposed might participate, through the vasoconstrictive actions of the hormone, in the cardiovascular and renal complications of DM.…”