Salt retention

Human growth hormone is a very complex molecule biologically. Several diverse biological activities such as anaboHc, insulin-like, diabetogenic, and lactogenic activities have been ascribed to hGH, which also appears to promote water and salt retention. An in-depth discussion of these activities may be found in several excellent reviews available in the Hterature (34—36). 

Fig. 12. Salt retention by coUoidal particles. The curved dashed and soHd lines represent the surface of a negatively charged siUca particle. Around this there is a layer of counter sodium cations outside there is a layer in which sulfate anions (Q) are more concentrated than in the bulk solution.

Natriuretic peptides are a family of peptide hormones. All of them contain a 17-amino acid long ring that is closed by a disulfide bond between two cysteine residues. ANP (atrial natriuretic peptide) is mainly expressed in the atria of the heart, whereas BNP (B-type natriuretic peptide) is synthesized in the ventricular myocardium. CNP occurs mainly in the endothelium and is thought to have a paracrine function. ANF and BNF lower blood pressure by a direct effect on smooth muscle and on the salt retention in the kidney. Natriuretic peptides bind and activate particulate guanylyl cyclases. 

Table 6 shows the efficiency of the RO unit. 99.9% salt retention is reached additionally reduction efficiencies of 99% for TDS, silica and conductivity, 95% for... 

Membranes RO membranes are designed for high salt retention, high permeability, mechanical robustness (to allow module fabrication and withstand operating conditions), chemical robustness (to fabrication materials, process fluids, cleaners, and sanitizers), low extractables, low fouling characteristics, high capacity, low cost, and consistency. 

Oxidant Removal The presence of oxidizers such as chlorine or ozone can degrade polyamide RO membranes, causing a drop in salt retention. Cellulosic membranes are less sensitive to attack. Addition of 1.5 to 6 mg sodium bisulfite/ppm chlorine or contacting with activated carbon will remove oxidizers. Vacuum degassing with a hydrophobic filter module is also used. 

Glucocorticoids Adrenal suppression, salt retention, diabetes,... 

Salt retention, by colloidal silica and silica sols, 22 392 Salt roasting... 

This membrane demonstrated a vastly improved flux compared with the poly(piperazine isophthalamide) membrane, but its seawater salt rejection was low — in the range of 60 to 70 percent. A reverse osmosis test with a magnesium sulfate feedwater showed greater than 99 percent salt retention, however, dispelling the possibility that low sodium chloride rejections were due to defects in the polyamide barrier layer. The piperazine polyamide was soon concluded to have the following structure (see Reaction 111). 

The adrenal glands secrete over 50 different steroids, the most important of which are aldosterone and hydrocortisone. Aldosterone causes salt retention in the body. It is not commercially available. Hydrocortisone is useful for its anti-inflammatory and antiallergic activity. Cortisone and its derivatives have similar activity and it is reduced in vivo to hydrocortisone. The two substances are used to treat rheumatoid arthritis. The 11-P-hydroxyl of hydrocortisone is believed to be of major importance in binding to the receptors of enzymes. Anti-inflammatory activity is significantly Increased by various substituents 6a-fluoro, 9a-fluoro, 21-hydroxy, 2a-methyl, 9a-chloro, and a double bond at C-1. 

Refractory fluid retention rarely may require discontinuation of minoxidil. Under close medical supervision, it may be possible to resolve refractory salt retention by discontinuing the drug for 1 or 2 days, and then resuming treatment in conjunction with vigorous diuretic therapy. 

Cardiovascular safety. Both drug types promote salt retention, can exacerbate heart failure and tend to raise blood pressure. COX-2 selective drugs also appear to raise the risks of thrombotic events, notably stroke and myocardial infarction, and recent evidence suggests that non-selective NSAIDs also raise these risks, though it is unclear whether to the same degree. For both drug types, dose and duration of treatment appear to affect risk. 

Adverse effects include nasal congestion, flushing, bradycardia, postural hypotension, water and salt retention and CHF may be precipitated. 

Despite intensive study, the pathophysiology of idiopathicedema (fluctuating salt retention and edema) remains obscure. Some studies suggest that intermittent diuretic use may actually contribute to the syndrome. Idiopathic edema should probably be managed with moderate salt restriction alone if possible. 

It is the rate of separation rather than the efficiency of salt retention that is the primary practical issue in the development of reverse osmosis desalination. In addition to a variety of other factors, the rate of reverse osmotic flow depends on the excess pressure across the membrane. Therefore the problem of rapid flow is tied into the technology of developing membranes capable of withstanding high pressures. The osmotic pressure of sea water at 25 °C is about 25 atm. This means that no reverse osmosis will occur until the applied pressure exceeds this value. This corresponds to a water column about 840-ft high at this temperature. 

Progestogens with a degree of mineralocorticoid activity will tend to cause water and salt retention and to increase blood pressure in susceptible subjects. However, effects on blood pressure can be variable for example, medroxyprogesterone has been variously reported to cause a fall in blood pressure in some initially hypertensive patients while rapidly increasing diastolic pressure in some other women, or to have no effect on blood pressure at all. 

However, the new compounds still possessed salt retention disadvantages. Nevertheless, the Squibb groups findings, coupled with other beneficial discoveries (see below), set off an enthusiastic stampede for superior anti-inflammatory steroids. 

In 1951-1952, Sulzberger et al. showed that systemically - but not topically -applied cortisone acetate was effective in the treatment of eczema and other der-matitides, whereas hydrocortisone was effective with both routes of administration [8,9]. Because the topical route promised a relative freedom from troublesome systemic side effects (e.g., salt retention). Schering recognized the need for an effective synthesis of the latter. 

Enhanced glucocorticosteroid activity (three to five times that of cortisone) and reduced mineralocorticoid activity at the projected therapeutic dose were demonstrated by the collaborators of Schering Corporation using appropriate assays. Anti-arthritic activity and the absence of any significant associated salt retention were quickly demonstrated for both prednisone and prednisolone. 

This earliest of the important enhancement discoveries was in itself not of therapeutic value, due to salt retention, yet it became a component in nearly all of the ultrapotent corticoids to be marketed. Indeed, it is why the discovery of the potent 9-fluoro-hydrocortisone was an event that had far-reaching significance. 

Introduction of the 16a-hydroxyl group into 9-fluoro-hydrocortisone and 9-fluoro-prednisolone has been shown by Bernstein et al. [16] to result in complete suppression of the salt-retaining properties of these steroids, without appreciably impairing their glucocorticoid activity. Moreover, studies in man have demonstrated the anti-arthritic activity of 9-fluoro-16a-hydroxy-prednisolone and have confirmed its lack of salt-retaining activity. Subsequently, Lederle reported that the anti-inflammatory potency was lowered, but salt retention was eliminated. 

Introduction of the 6a-methyl group into prednisolone produced a compound which is more active than prednisolone, and with a better therapeutic index with respect to salt retention. 

Ultraviolet graft polymerization of arylamide onto cellulose acetate reverse osmosis membranes yielded grafted membranes with higher salt retention and lower water flux compared with pristine cellulose acetate [152]. Acid-catalyzed grafting of styrene on cellulose acetate reverse-osmosis membranes imparted a higher salt rejection rate (92.4%) to the membrane than those of ungrafted membranes (80.8%) and heat-shrunk membranes (90.2%) [153]. 

NS AIDs CALCIUM CHANNEL BLOCKERS 1 antihypertensive effect of calcium channel blockers NSAIDs cause salt retention and vasoconstriction at possibly both renal and endothelial sites Monitor BP at least weekly until stable... 

Membrane constituent pH of soaking solution Salt retention coefficient (%) Water permeation rate(cm -cm -hr ... 

Fluid and salt retention have been observed in small children given metamizole (2). 

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