Adrenocorticotropic hormone norepinephrine

Otfier fiormones accelerate tfie release of free fatty acids from adipose tissue and raise tfie plasma free fatty acid concentration by increasing the rate of lipolysis of the triacylglycerol stores (Figure 25—8). These include epinephrine, norepinephrine, glucagon, adrenocorticotropic hormone (ACTH), a- and P-melanocyte-stimulat-ing hormones (MSH), thyroid-stimulating hormone (TSH), growth hormone (GH), and vasopressin. Many of these activate the hormone-sensitive hpase. For an optimal effect, most of these lipolytic processes require the presence of glucocorticoids and thyroid hormones. These hormones act in a facilitatory or permissive capacity with respect to other lipolytic endocrine factors. 

Hydroxytryptamine (5-HT), dopamine, and norepinephrine play important roles as central neurotrans-mitters in the process of erection. Still other substances or hormones, such as endorphins, oxytocin, vasopressin, adrenocorticotropic hormone (ACTH) and related peptides, and prolactin, appear to participate in the complex and coordinated process of penile erection. Central nonadrenergic neurons also may influence male sexual behavior. 

The initial event in the utilization of fat as an energy source is the hydrolysis of triacylglycerols by lipases, an event referred to as lipolysis. The lipase of adipose tissue are activated on treatment of these cells with the hormones epinephrine, norepinephrine, glucagon, and adrenocorticotropic hormone. In adipose cells, these hormones trigger 7TM receptors that activate adenylate cyclase (Section 15,1.3 ). The increased level of cyclic AMP then stimulates protein kinase A, -which activates the lipases by phosphorylating them. Thus, epinephrine, norepinephrine, glucagon, and adrenocorticotropic hormone induce lipolysis (Figure 22.6). In contrast, insulin inhibits lipolysis. The released fatty acids are not soluble in blood plasma, and so, on release, serum albumin binds the fatty acids and serves as a carrier. By these means, free fatty acids are made accessible as a fuel in other tissues. 

Nicotine binds selectively to the nicotinic receptors that are present in the adrenal medulla, brain, autonomic ganglia, and neuromuscular junctions. It causes the release of several neurotransmitters and hormones such as acetylcholine, norepinephrine, dopamine, serotonin, arginine vasopressin, j3-endorphin, adrenocorticotropic hormone, and cortisol (187). This neuro-regulatory effect of nicotine is dose-dependent and occurs as plasma nicotine level rises when tobacco is smoked. The neurotransmitters released in the brain medi-... 

The adrenal glands, which are divided into the medulla (core) and the cortex (outer layer), furnish catecholamines and steroids, respectively. The catecholamines are hormonally active, and consist of norepinephrine and epinephrine. Steroids variously affect carbohydrate, protein, and lipid metabolism, regulate the sall/water losses of the kidneys, and affect sexual development and function. Androgens and estrogens fall in the last-mentioned category. Another adrenal hormone of note is ACTH, or adrenocorticotropic hormone. Cortisol is an adrenal product, which can be converted to cortisone. 

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