Rectal gland

The physiological role of the ICOR is not clear and may be heterogeneous in the various tissues. In the thick ascending limb of the loop of Henle this channel appears to serve as the exit for CP at the basal cell pole [16,65,66], This conductive mechanism, therefore, is required for the reabsorption of Na and CP by this segment of the nephron [16]. In the rectal gland of Squalus acanthias a very similar channel is utilized for Na" and CP secretion. In these latter cells the CP-channel is present in the luminal membrane and is controlled by cytosolic cAMP [15,56,71]. It has been claimed that this kind of channel is also responsible for the secretion of CP in the colonic crypt cell, in colonic carcinoma cells and in respiratory epithelial cells [17,19,20,22]. Recent data have cast some doubt on this concept ... 

CP-channels with smaller conductance have first been noted in the rectal gland of Squalus acanthias by ourselves and in the colonic carcinoma cell line HT29 [61,73]. Later these types of 5-15 pS CP-channels were also found in pancreatic ducts, A6-cells and many other cells [74,75]. It is now claimed that this kind of channel is much more relevant than the ICOR for the pathophysiology of cystic fibrosis [12]. 

I have noted that NPPB is structurally related to loop diuretics of the furosemide (Fig. 2) type. These latter compounds bind to the Na 2CNK -cotransporter [16] and inhibit NaCl reabsorption in the TAL segment and NaCl secretion in epithelia such as the colonic crypt cell and rectal gland of Squalus acanthias [15]. We were able to show that only minor modification of the NPPB molecule on one side and of furosemide on the other led to compounds with altered selectivities [70,91-93]. One prototype of an intermediate blocker, i.e., a substance blocking both Na 2Cl K -cotransport and CP-channels, is torasemide (Fig. 2). Hence we have performed a systematic study in order to define the constraints defining the effectiveness of this class of substances [91]. 

Silva, P., F.H. Epstein, and R.J. Solomon. 1992. The effect of mercury on chloride secretion in the shark (,Squalus acanthias) rectal gland. Comp. Biochem. Physiol. 103C 569-575. 

The cis-Pt compound showed some selective uptake into -SH abundant tissues such as kidney, muscle and rectal gland (data not shown) but not RBC s. Most other tissues showed no remarkable concentration and/or increased percentage of dose retained over those expected from uniform distribution. There was moderate CNS penetrance of cis-Pt. Neither the Hg nor Pt compound appeared in... 

The volatiles of the pH 4.2 bait are dominated by aldehydes and ketones while those of the pH 9 bait are dominated by pyrazines. Figure 5 shows the structures of some of these pyrazines. It is interesting to note that some of these pyrazines have also been found in the rectal gland secretion of the male melon fly (77). 

Fanelli, R., Gariboldi, P., and Verotta, L. 1983. Studies on the sex pheromone of Dacus oleae. Analysis of the substances contained in the rectal glands. Experientia, 39(5) 502-5. 

Silva, P Mount Desert Island Biological Salsbury Cove, ME Mercury in chloride transport in shark rectal gland and rabbit thick ascending limb. NIEHS... 

Nishida R et al (1988) Accumulation of phenypropanoids in the rectal glands of males of the oriental fruit fly, Dacus dorsalis. Experientia 44 534-536... 

Miller, D.S., R. Masereeuw, J. Henson and K.J. Kamaky. Excretory transport of xenobiotics by dogfish rectal gland tubules. Am. J. Physiol. 275 R697—R705, 1998. 

Some ant species (Formicidae) use nitrogen heterocycles as trail pheromones others however use hydrocarbons or alcohols (Fig. 8.62). In the rectal glands of a few Lasius and Formica species, 3,4-dihydroisocoumarins have been identified. The scents are emitted by exocrine glands like the poison apparatus or the sternal gland. The trail pheromone of the leafcutter ant (Atta texana) is effective at extremely low concentrations of 80 fg/cm (If = 10" ). One milligram of methyl 3-methylpyrrole-2-carboxylate is sufficient to lay a trail three times around the Earth. 

Rectal gland secretion from male melon flies (Dacus cucurbitae). Pharmaceutical aid, antifungal agent. Preservative. Cryst. Mp 116°. Bp 297-298° dec. pX j 8.50 (25°). 

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