Effect of noradrenaline on plasma hormones and metabolites in cold-acclimated rats.

Abstract

The effects of noradrenaline (NA) injection (40µg/100g, i.p.) on plasma glucagon, corticosterone (CS), deoxycorticosterone (DOCS), glucose, and free fatty acids (FFA) were investigated in cold-acclimated rats (CA) and warm controls (WC). The CA were transferred to warm control temperature ca. 18 h prior to NA or saline injection. The animals were decapitated and the trunk blood was collected 0, 10, 20, and 40 min after the injection. Plasma glucagon level increased significantly during the experimental period after NA, while saline did not influence its level. The magnitude of increase as assessed by 95% confidence interval was significantly greater in CA than in WC. Plasma CS and DOCS were significantly increased by saline injection, but NA caused greater elevations of these steroid-hormones. The magnitudes of increases were also greater in CA. In contrast to the hormonal responses, NA-induced increases of plasma glucose and FFA levels were smaller in CA than in WC. These results suggest that glucagon and glucocorticoids are released, at least partly, by NA, and these thermogenic factors act in synergism, enhancing nonshivering thermogenesis through an accelerated utilization of energy substrates such as glucose and FFA.

Metabolic cold acclimation after repetitive intermittent cold exposure in rat.

“…The increase of BAT weight did not differ between ICE and CA, although the increases in fat-free dry matter fraction and glucagon level of BAT were smaller in ICE than in CA. A possible role of glucagon in metabolic cold acclimation has been recently reported from our laboratory (KuROsHIMA et al, 1978(KuROsHIMA et al, , 1984(KuROsHIMA et al, , 1988 and also others (BILLINGTON et al, 1987;HOWLAND and BOND, 1987). The present study confirmed the previous results that glucagon level was higher in BAT from CA even in the resting state (HABARA and KUROSHIMA, 1983;, suggesting that glucagon exerts its thermogenic effect on BAT in high concentration.…”

Noradrenaline-induced changes in rat brown adipose tissue glucagon.

“…Figure 1 shows the changes in plasma glucagon levels after NA injection. The result was essentially the same as reported previously (KUROSHIMA et al, 1988). The initial level was significantly lower in CA.…”

“…It was noted in the present study that plasma glucagon level was restored to the initial level in WC during the experimental period for 40 min, while it remained still higher than the initial level in CA. This finding, together with the previous one (KUROSHIMA et al, 1988) clearly indicates an enhanced action of NA on glucagon release, suggesting a possible involvement of this pancreatic hormone secreted by NA in an enhanced NST in concert with NA during cold acclimation.…”

“…Pancreatic glucagon has also been claimed to be involved in the regulation of this specific heat production during cold acclimation (KUROSHIMA et al, 1984). Recently it was interestingly noted that glucagon was released when NST was stimulated by NA and its degree was significantly potentiated in the coldacclimated rats (KUROSHIMA et al, 1988). Thus this finding suggests that glucagon released by NA would participate, at least in part, in an enhanced NST during cold acclimation in concert with NA.…”

Unstressing intemperate models: how cold stress undermines mouse modeling

“…Adaptation to cold stress involves, among other things, glucocorticoid production and sustained activation of the sympathetic nervous system (Leduc, 1961; Shum et al, 1969; Yahata et al, 1987; Kuroshima et al, 1988; Ohno et al, 1990; Gordon, 1993; Harper and Austad, 2000; Cannon and Nedergaard, 2004, 2011; Feldmann et al, 2009; Baccan et al, 2010). The immunosuppressive effects of glucocorticoids are widely appreciated, and activation of the sympathetic nervous system has broad effects beyond driving adaptive thermogenesis and supporting processes such as heart rate and cardiac output.…”