Tubular secretion is : The process in which ions and other waste products are transported into the distal tubules of the nephron.
can it be regarded as local hormone??
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First of all, I can't understand how can you regard an electrochemical process (tubular secretion) as chemical substance (hormone).
Tubular secretion is the transfer of materials from peritubular capillaries to renal tubular lumen. Tubular secretion is caused mainly by active transport. Usually only a few substances are secreted. These substances are present in great excess, or are natural poisons. Many drugs are eliminated by tubular secretion [1].
The substances that are secreted into the tubular fluid (for removal from the body) include [2]:
- Potassium ions (K+),
- Hydrogen ions (H+),
- Ammonium ions (NH4+),
- creatinine,
- urea,
- some hormones, and
- some drugs (e.g. penicillin).
Tubular secretion occurs from the epithelial cells that line the renal tubules and collecting ducts [2].
Uptake transporters in the basolateral membrane and export transporters in the luminal membrane of renal tubule cells are involved in tubular secretion of their substrates (organic anion transporters and organic cation transporters - these are transmembrane proteins) [3].
Despite considerable advances in the understanding of basic transport pathways and mechanisms involved in the tubular secretion of organic compounds, there is still relatively little information on the regulation of this transport [4].
References:
Wikipedia contributors, "Renal physiology," Wikipedia, The Free Encyclopedia, http://en.wikipedia.org/w/index.php?title=Renal_physiology&oldid=608689347 (accessed June 26, 2014).
http://www.ivy-rose.co.uk/HumanBody/Urinary/Urinary_System_Kidneys_Actions_3.php
Müller F, Fromm MF. Transporter-mediated drug-drug interactions. Pharmacogenomics. 2011 Jul;12(7):1017-37. doi: 10.2217/pgs.11.44. PubMed PMID: 21787191.
Berkhin EB, Humphreys MH. Regulation of renal tubular secretion of organic compounds. Kidney Int. 2001 Jan;59(1):17-30. doi: 10.1046/j.1523-1755.2001.00461.x. PubMed PMID: 11135053.
