Fine structure of the rectal (salt‐secreting) gland of the spiny dogfish, Squalus acanthias

Abstract

The rectal gland of the spiny dogfish, Squalus acanthias has been described by light and electron microscopy. The cell outline shows remarkable complexity in electron micrographs. The basal plasma membrane has numerous complex infoIdings and interdigitations separated by groups of mitochondria. The lateral plasma membrane also shows extensive interdigitation. The apical region demonstrates profiles of interleafing cell processes with much membrane interdigitation occurring between them but containing few mitochondria. The apical surface has microvilli which extend into the tubular lumen and are covered with nap-like filaments. Glands of some fish were catheterized and attempts were made to correlate the fine structure of these glands with the known secretory rates. The cellular morphology of the secretory cells of the rectal gland correlates well with that seen in other ion-transporting tissues, although some unique specializations were noted.Ion transport pervades all of biology. In spite of efforts by scientists of many fields, the basic mechanisms of ion accumulation and pumping remain unknown. One approach to the problem of salt secretion is to examine the structure of cells which are highly specialized for this activity. The rectal gland of the spiny dogfish, Squalus acanthias, is such a tissue. Burger and Hess ('60a, b ) catheterized the duct of the gland and have shown that this gland was capable of secreting a sodium chloride solution with a concentration about twice that of the blood plasma and greater than that of sea water. They also showed that the volume of fluid excreted was large enough to eliminate significant amounts of sodium chloride from the fish, this presumabIy being its function. Burger ('62) also demonstrated that the gland secreted at a greater rate after the fish received a large dose of salt solution. He could find no evidence of neural control.Important articles from the older literature on the anatomy and physiology of elasmobranch rectal glands were those of Pilliet (1885), Crawford (1899), Hoskins ('17), and Crofts ('25). The recently published physiological studies proposing a salt-excreting function have awakened a new interest in the morphology of this gland. Abstracts have been published on the histochemistry of elasmobranch rectal glands by Bernard and Hartmann ('60) on the histology and ultrastructure of rectal glands from Squalus acanthias by Bulger ('61) and on the ultrastructure of the glands of Urolophus (round sting-ray) by Doyle ('62a). IR addition, Doyle ('6%) recently published an article on the fine structure of the secretory cells of Urolophus with comments on the structure seen in Squalus acanthias.Various structures have been associated with the function of salt secretion, but no unique structure has been identified with certainty as being responsible for salt concentration. Rather, it appears that the rectal gland, in general, resembles the structure, both coarse and fine, of other electrolyte-separating organs. This paper substantiates such a concl...

Regulation of Na,K-ATPase by PLMS, the Phospholemman-like Protein from Shark

“…Immunolocalization of PLMS and Na,K-ATPase ␣-SubunitThe rectal gland is composed of winding tubules formed by tall columnar cells arranged around a central duct or lumen as previously described (45)(46)(47). The luminal cell surface exhibits only a few small microvilli (Fig.…”

Scanning and transmission electron microscope studies on the organ of corti and stria vascularis in human fetal cochlear ducts.

“…The fine structure of the stria vascularis has been observed in various mammals by many authors (ENGSTROM, SJOSTRAND and SPOENDLIN, 1955;SMITH, 1957;CHOU, 1961;YAMAMOTO and NAKAI, 1964;RODRIGUEZ-ECHANDIA and BURGOS, 1965;HINOJOSA and RODRIGUEZ-ECHANDIA, 1966 active transport of ions has been reported in salt secreting cells (DOYLE, 1960;BULGER, 1963;PHILPOTT and TEMPLETON, 1964) and in chloride cells (PHILPOTT and COPELAND, 1963;CONTE, 1969). In the cochlear duct, RODRIGUEZ-ECHANDIA and BURGOS (1965) have suggested that the unusually high concentration of potassium ions in the endolymph is due to the presence cf a specialized structure somewhere in the stria vascularis for secretion of this ion.…”

On the Fine Structure of the Terminal Portion of Nasal Gland in Guinea Pig, with Special Reference to the Interrelationship between Glandular Cells and Nerve Endings

“…Similar structural specialization of cell surface has been reported in the epithelium of the salivary glands (SCOTT and PEASE 1959, others), of the sweat gland (HIBBS 1958, others), and of urinary tubules which are well known to be involved in the vigorous water transport (PEASE 1956). Furthermore, it is known that some salt-secreting cells in the lower vertebrates also show similar specialization of lateral surface (DOYLE 1960, BULGER 1963. Recently SOROKIN (1965) has described in the bronchial gland of opossum the hydrotic cell, the lateral surfaces of which are provided with the extensive cytoplasmic folds similar to those of nasal glandular cell.…”