Extracellular compartments

However, it is clear that the resting compliance is relatively more important to the springlike behavior of many active smooth muscles. Each smooth muscle must be analyzed individually since the extracellular compartment of each smooth muscle as a histological entity is different. 

Since Cu ions can catalyse formation of the dangerous hydroxyl radical, its concentration in both the intra- and extracellular compartments is maintained at very low levels by binding to the protein metallothionine. Deficiency of copper results in defects in formation of connective tissue, which may cause cardiovascular problems and poor bone formation. 

Enclosure and insulation of cells and organelles. The enclosure provided by the plasma membrane protects cells from their environment both mechanically and chemically. The plasma membrane is essential for maintaining differences in the concentration of many substances between the intracellular and extracellular compartments. 

The major adverse reactions associated with mannitol administration are headache, nausea, vomiting, chest pain, and hyponatremia. Too rapid an administration of large amounts may cause an excessive shift of fluid from the intracellular to the extracellular compartment and result in congestive heart failure. 

Excessively vigorous diuresis may lead to intravascular dehydration before removal of edema fluid from the rest of the extracellular compartment. This is especially dangerous if the patient has significant liver or kidney... 

Monoamine oxidase inhibitors inhibit serotonin inactivation in the extracellular compartment, just as they inhibit catecholamine inactivation. 

Mannitol is rapidly distributed in the extracellular compartment and extracts water from cells. Prior to the diuresis, this leads to expansion of the extracellular volume and hyponatremia. This effect can complicate heart failure and may produce florid pulmonary edema. Headache, nausea, and vomiting are commonly observed in patients treated with osmotic diuretics. 

The composition of the extracellular compartment is kept constant by the cooperation of the cellular transport systems with various transport systems which are located in epithelial layers connecting the organism with its environment (Table 1). Examples are the epithelia of the intestine, the kidney and of various glands. It is their function to establish a relatively constant concentration of the respective solutes... 

Fig. 3. Proposed mechanism involving hydrolytic and synthetic activities of glucose-6-phosphatase in the transport of glucose between intracellular and extracellular compartments. The shaded area represents the cross-sectional view of endoplasmic reticulum. E and E" are modified forms of glucose-6-phosphatase displaying principally phosphohydrolase and principally phosphotransferase activities, respectively. Differential influences of the intra- and extracellular milieu are postulated to maintain molecules of the enzyme selectively as E or E". Additional details are given in Section II,D.

OHSS is characterized by cystic ovarian enlargement, increased capillary permeability, and third space fluid accumulation (that is in an extracellular compartment that is not in equilibrium with either the extracellular or intracellular fluid, for example the bowel lumen, subcutaneous tissues, retroperitoneal space, or peritoneal cavity). Risk factors include a previous history of OHSS, age under 30 years (probably because more follicles are available), and polycystic ovary syndrome. Non-pregnant patients usually recover within 14 days with supportive treatment. The severe form (with ascites or pleural effusion and hemoconcentration) occurs in 1-10% of patients (64,65). In critical cases, hypoxemia, renal insufficiency, thromboembolism, and rarely death can occur (66). 

Cirsiliol, a flavone isolated from the species Achillea fragantissima, causes a concentration-dependent relaxation of isolated ileum, interferes with calcium channels, and thus inhibits Ca2+ influx from the extracellular compartment. Its therapeutic efficacy is not known. 

Recent studies have shown that the binding of ligands to GPIIb/llla also activates a number of cellular processes important for platelet stimulation (50) including the synthesis of 3-phosphorylated phosphatidylinositols, the release of arachidonic acid, and the increase in plasma calcium levels. Stimulation of these processes allows for bidirectional signaling between the intracellular and extracellular compartments. 

As shown in Table HI, sucrose enters nutritionally normal cells only to a slightly greater extent than dextran and inulin, which are confined to the extracellular compartment. The small differences between these values may arise from the more complete distribution of sucrose in cell wall interstices. In contrast, glycerol, a substance which is known to enter many cells rapidly and which does not stimu-... 

---