Effects of thyroid and growth hormone deficiency, and food restriction on heart mass, with and without added stress (carboxyhemoglobinemia)

Abstract

The roles of thyroid and growth hormone, and food restriction in maintenance of heart mass and in carbon monoxide-stimulated cardiac growth were examined. First, thyroidectomized and normal adult male rats inhaled up to 500 ppm CO in air for 42 days. Combined ventricular weights of thyroidectomized rats inhaling CO and air were 12 and 23% smaller than predicted, respectively, while the combined ventricular weight of normal rats inhaling CO was 29% larger than predicted. Thyroidectomy increased the mass of the left ventricle relative to the right ventricle; this was reversed by CO treatment. While the hematocrit increased in thyroidectomized-CO rats, it was lower than in normal-CO rats: likewise the hematocrit of thyroidectomized-AIR rats was lower than that of normal rats in air. Body weights of the thyroidectomized rats were 57% that of normals. As additional controls, two groups of normal rats (one AIR, one CO) were maintained at the same body weight as the thyroidectomized rats, by adjusting food intake. Combined ventricular weight was less than predicted in AIR rats and failed to increase in CO animals, while hematocrits were the same as normals in air and in CO. Serum thyroxine (T4) and growth hormone levels assayed in thyroidectomized rats were less than 15 and 25% of normal rats, respectively. Growth hormone levels were not altered by CO inhalation in thyroidectomized and in normal rats. Levels of both hormones were normal in food-restricted rats. While thyroidectomy produced cardiac atrophy, cardiac growth was stimulated by CO inhalation, although heart mass then only approached that of normals in air. Food restriction also produced cardiac atrophy, but CO inhalation failed to stimulate heart growth.

Thyroid receptor plasticity in striated muscle types: effects of altered thyroid state

“…The low T 4 levels in this group were attributed to a T 3 -induced inhibition in T 4 production due to the high levels of circulating T 3 . The absolute and relative heart weight data paralleled the T 3 data (Table 1), which provides strong evidence of an altered thyroid state, as the increases and decreases in these values relative to the euthyroid state are characteristics of a hyperthyroid and hypothyroid state, respectively, in rodents (18,30).…”

Effects of nicotine on heart dimensions and blood volume in male and female rats

“…Alternatively, nicotine might be exerting its effects on the heart through reductions in food consumption. Nicotine reduces food consumption (Grunberg 1982;Grunberg et al, 1986Grunberg et al, , 1987, and food restriction reduces organ mass, including heart size (Penney & Barthel, 1985). This possible mechanism for nicotine's effects on the heart is only partially supported by the results of the present experiment.…”

Repeated Acute Stress Alters Heart Morphometry in Male and Female Rats Differently

“…Stress reduces food consumption and food restriction reduces organ mass, including heart size (Penney and Barthel, 1985). This possible mechanism for stress effects on the heart is only partially supported by the results of the present experiment.…”