Disease relevance of Portal System

• The development of implantable insulin pumps, which can deliver insulin intraperitoneally, led to numerous studies on insulin-dependent diabetes mellitus (IDDM) patients, demonstrating that insulin delivered intraperitoneally is rapidly and predictably absorbed with most of it going into the portal system, resulting in hepatic delivery of insulin [1].
• The resistance of mice with schistosomiasis that were injected with trehalose dipalmitate and challenged with schistosomal cercariae was increased, as assayed by recovery of schistosomula from the lungs and of adult worms from the portal system [2].
• PVA particles and coils were used to occlude the right portal system and veins supplying segment IV to promote FLR hypertrophy (segments I-III +/- IV) [3].
• Hypothyroidism presumably increases the release of DA into the pituitary portal system [4].
• With reactive hyperemia both significant higher peak iodine concentrations in the portal blood and significant improvement in visualization of the portal system and porto-systemic venous collaterals occurred when compared to tolazoline or control angiograms [5].

High impact information on Portal System

• Retinoic acid is mainly absorbed through the portal system and transported in plasma as the anion bound to serum albumin [6].
• Thus despite massive histological alterations and pronounced increases in stimulation-dependent resistances - predominantly in the portal system - cirrhotic rat livers responded in their glucose metabolism to nervous and hormonal stimuli in almost the same manner as normal livers [7].
• Theoretically peri-insular levels depend on the islet-acinar portal system, but the actual hormone levels have never been demonstrated [8].
• Taken together, these results show that AL POMC cells possess functional regulatory receptor systems prior to maturation of the hypothalamic-hypophyseal portal system [9].
• We also propose that stress-induced CRH release will not be similarly quenched by the CRH-BP in the hypothalamic portal system, as the concentration of CRH released will be high, and the exposure time before reaching pituitary corticotropes will be low [10].

Chemical compound and disease context of Portal System

• Nitroprusside absorbed into the portal system did not cause hypotension, as is usual with systemic administration, because nitroprusside is inactivated by passage through the liver [11].
• This may be due to the fact that in diabetes insipidus AVP secretion from parvocellular neurons of the paraventricular nucleus in the hypophysial portal system is not impaired.(ABSTRACT TRUNCATED AT 250 WORDS)[12]
• The conclusions of this study may be only preliminary owing to both the insufficient period of observation and the small number of rats, but the inhibitory effect of 5-FU on the development of liver metastases was disappointing as a result of the large number of tumor cells injected into the portal system [13].
• BACKGROUND: Little is known about the role of the CO2 pneumoperitoneum on tumor cells that spread from the portal system into the liver during laparoscopic surgery for gastrointestinal malignancies [14].

Biological context of Portal System

• Evaluation of intestinal absorption into the portal system in enterohepatic circulation by measuring the difference in portal-venous blood concentrations of diclofenac [15].
• The local absorption kinetics from the intestinal tract into the portal system was evaluated using the portal-venous concentration difference (P-V difference) after oral administration of diclofenac in conscious rats [16].
• When 1.5-3 micrograms histamine (free base) was infused into the portal system, portal venous pressure rose from 15.2 +/- 0.33 to 24.8 +/- 0.40 cmH2O (p < 0.05) (1 cmH2O = 98.1 Pa) [17].
• However, increased sensitivity to catecholamine-induced lipolysis of the Gly allele promotes higher free fatty acids concentrations in the portal system, which could enhance the higher levels of fasting insulin [18].
• Peripheral infusion of SRIF at a rate to provide concentrations comparable to those in the portal system leads to a desensitization of SRIF effects on the somatotroph, likely mediated by down-regulation of SRIF receptors [19].

Anatomical context of Portal System

• We conclude that Cudt containing TEPA depletes exocrine tissue and facilitates pancreas digestion for successful transplantation of islets into the portal system [20].
• The release of CRF into the hypothalamic-hypophyseal portal system in response to stress is known, and it has been suggested that CRF may function elsewhere in the central nervous system to promote stress-induced physiological and behavioral changes [21].
• Both ascorbic acid and hydrocortisone are secreted from cortical cells during stress into the adrenal portal system and thus contact medullary chromaffin cells [22].
• The results demonstrate that the axon of some neuroendocrine CRF cells in the rat paraventricular nucleus give rise to terminal boutons just outside the nucleus, and may thus synapse with other hypothalamic neurons, as well as releasing neuropeptides into the hypophyseal portal system [23].
• An immunoreactive (IR) LHRH-producing system, with perikarya located in the preoptic nucleus, could be traced through the ventral hypothalamus down to the external layer of the rostral and caudal ME, in close vicinity to the hypophysial portal system [24].

Associations of Portal System with chemical compounds

• In this study we tried to determine if there is accumulation of prostacyclin in the portal system [25].
• CONCLUSIONS: Treatment with a liver-specific NO donor improves the portal system adaptability to portal blood flow increase and ameliorates the intra-hepatic response to methoxamine in cirrhotic rats [26].
• If some chromium(VI) is absorbed by the intestine, it is massively reduced in the blood of the portal system and then in the liver [27].
• In contrast, infusion of insulin (1.0 mU/kg X min) and glucagon (4 ng/kg X min) into the portal system did not alter hepatic extraction of insulin even though the amounts of insulin and glucagon presented to that organ were similar to those obtained with arginine and CCK-PZ [28].
• This value was within the reported steroid concentration in the adrenal portal system during a significant stress [22].

Gene context of Portal System

• Hypothalamic GHRH is secreted into the portal system, binds to specific surface receptors of the somatotroph cell and elicits intracellular signals that modulate pituitary GH synthesis and/or secretion [29].
• ET-1 (45 ng, i.c.v.) also produced a significant reduction in blood flow to the brain (75%), heart (49%), kidneys (66%), GIT (40%), portal system (52%) and musculo-skeletal system (38%), while blood flow to the skin was not affected [30].
• These results suggest that CEA may be drained mainly by the hematogenous portal system by the draining vein from the cancer cells in the invasive veins and that CA19-9 may be drained by the thoracic duct of the lymphatic system [31].
• Hormones classically considered confined to the magnocellular-neurohypophysial system are found in the parvocellular-long portal system and are known to be paramount in the hypophysiotropic control of ACTH release [32].
• Thus, we found no evidence that arcuate NKB neurons project to the primary capillary plexus of the portal system [33].

Analytical, diagnostic and therapeutic context of Portal System

• Increased perfusion was also seen when epinephrine was administered through the portal system, and in larger tumors after intraarterial administration [34].
• As eggs accumulated in the liver and portal hypertension increased, the number of injected microspheres escaping from the hepatic portal system rose in rank order of diameter from 9 microns through 15 microns and 25 microns to 50 microns [35].
• CONCLUSION: CO2 splenoportography is safe and expedient and provides adequate visualization of the portal system for surgical planning in selected patients [36].
• Results are nearly the same with superior mesenteric vein-inferior vena cava shunt, splenorenal shunt and portacaval shunt when the respective veins of the portal system are more than 1 cm in diameter [37].

References