Eccrine Sweat Gland Problem
This figure shows the basic structure of an eccrine sweat gland. As you can see, the secretory part indulges in NaCl secretion; the reabsorptive
duct dilutes the primary secretion by recovering NaCl. Sweating is mainly the result of cholinergic input; adrenergic input is less effective. Sweat
glands are innervated by sympathetic preganglionic fibers and the receptors on the secretory cells are muscarinic and beta2-adrenergic. The
most common diagnostic test for the disease cystic fibrosis is measurement of the salt concentration of sweat. Non-affected individuals make
sweat that is no more concentrated than 60 mEq/l, whereas that of affected individuals is as high as 120 mEq/l.
Sweat glands evolved in the early mammalian line. You have the following genes in your evolutionary toolbox. Using them, construct a plausible
hypothesis for arrangement of transporters in a sweat gland secretory cell and a sweat gland ductal cell. Just draw in each transporter on the cell
profile provided, label each transporter clearly with its identity, and show the type of ion transported and the direction that that ion is being
transported.
Na/K ATPase
NK2C transporter
Epithelial-type Na+ channel
CFTR channel
Secretory cell
“rest” K+ channel
sweat
Interstitial
fluid
Reabsorptive cell