Orotic acid is a minor dietary constituent. Historically it was believed to be part of the vitamin B complex and was called vitamin B13, but it is now known that it is not a vitamin and is synthesized in the body, where it arises as an intermediate in the pathway for the synthesis of pyrimidine nucleotides. Orotic acid is converted to UMP by UMP synthase, a multifunctional protein with both orotate phosphoribosyl transferase and orotidylate decarboxylase activity. The most frequently observed inborn error of pyrimidine nucleotide synthesis is a mutation of the multifunctional protein UMP synthase. As a result, plasma orotic acid accumulates to high concentrations, and increased quantities appear in the urine. Orotic acid levels are elevated in the urea cycle defects ornithine transcarbamylase (OTC) deficiency, citrullinemia and argininosuccinic acidemia, as well as the mitochondrial transport disorder hyperornithinemia-hyperammonemia-homocitrullinuria (HHH) syndrome. Orotic acid is also elevated in hereditary orotic aciduria, or uridine monophosphate synthase deficiency, an autosomal recessive disorder characterized by megaloblastic anemia and crystalluria. In addition, orotic acid in combination with leflunomide is in the phase II of clinical trial to evaluate the clinical efficacy and safety of a combination in kidney transplant patients with high levels of Polyoma BK viruria for the purpose of preventing polyoma BK viremia and nephropathy, that could lead to kidney transplant loss from viral damage, acute rejection or both.

Bradykinin, a pro-inflammatory mediator is also a neuromediator and regulator of several vascular and renal functions. Bradykinin can act as a vasoactive substance along with histamine in inflammation and swelling as it is a potent vasodilator. In addition, it triggers the release of other mediators such as nitric oxide in inflammatory and cancer tissues. Bradykinin acts via specific cell surface receptors: bradykinin receptor, B1 and B2 that are G-protein coupled receptors of the seven-transmembrane domain family. It was shown that increased plasma levels of bradykinin lead to the angioedema as the common major clinical manifestation. Bradykinin was also studied in heart transplant recipients and in obesity patients, but these studies were terminated or withdrawn for different reasons. Bradykinin is also an important growth factor for many cancers. Bradykinin antagonists showed higher potency than standard anti-cancer drugs, without evident toxicity to the hosts, that is why they have great promise for the development of new anti-cancer drugs.

Diquafosol, a dinucleotide Up4U, is an agonist for purinergic P2Y2 receptor. Diquafosol stimulated water and mucin secretion by acting on P2Y2 receptors on the conjunctival epithelial and goblet cell membrane and elevating intracellular calcium ion concentrations. The Japanese Ministry of Health, Labour and Welfare granted approval for DIQUAS Ophthalmic Solution 3% (diquafosol tetrasodium) for the treatment of dry eye.

Oteracil is an adjunct to antineoplastic therapy, used in combination with Gimeracil and Tegafur. Gimeracil/oteracil/tegafur combination is approved for the gastric cancer treatment. Oteracil is an orotate phosphoribosyltransferase (OPRT) inhibitor that decreases the activity of 5-fluorocil (tegafur is a prodrug of 5-fluorocil) in normal gastrointestinal mucosa.

Angiotensin is a peptide hormone that causes vasoconstriction and a subsequent increase in blood pressure. It is part of the renin-angiotensin system, which is a major target for drugs that lower blood pressure. Angiotensin also stimulates the release of aldosterone, another hormone, from the adrenal cortex. Aldosterone promotes sodium retention in the distal nephron, in the kidney, which also drives blood pressure up. Angiotensin is an oligopeptide and is a hormone and a powerful dipsogen. Angiotensin I is derived from the precursor molecule angiotensinogen, a serum globulin produced in the liver. Angiotensin I is converted to angiotensin II (AII) through removal of two C-terminal residues by the enzyme angiotensin-converting enzyme (ACE), primarily through ACE within the lung (but also present in endothelial cells and kidney epithelial cells). ACE found in other tissues of the body has no physiological role (ACE has a high density in the lung, but activation here promotes no vasoconstriction, angiotensin II is below physiological levels of action). Angiotensin II acts as an endocrine, autocrine/paracrine, and intracrine hormone. Angiotensin II has prothrombotic potential through adhesion and aggregation of platelets and stimulation of PAI-1 and PAI-2. When cardiac cell growth is stimulated, a local (autocrine-paracrine) renin-angiotensin system is activated in the cardiac myocyte, which stimulates cardiac cell growth through protein kinase C. The same system can be activated in smooth muscle cells in conditions of hypertension, atherosclerosis, or endothelial damage. Angiotensin II is the most important Gq stimulator of the heart during hypertrophy, compared to endothelin-1 and α1 adrenoreceptors. Angiotensin II increases thirst sensation (dipsogen) through the subfornical organ of the brain, decreases the response of the baroreceptor reflex, and increases the desire for salt. It increases secretion of ADH in the posterior pituitary and secretion of ACTH in the anterior pituitary. It also potentiates the release of norepinephrine by direct action on postganglionic sympathetic fibers. Angiotensin II acts on the adrenal cortex, causing it to release aldosterone, a hormone that causes the kidneys to retain sodium and lose potassium. Elevated plasma angiotensin II levels are responsible for the elevated aldosterone levels present during the luteal phase of the menstrual cycle. Angiotensin II has a direct effect on the proximal tubules to increase Na+ reabsorption. It has a complex and variable effect on glomerular filtration and renal blood flow depending on the setting. Increases in systemic blood pressure will maintain renal perfusion pressure; however, constriction of the afferent and efferent glomerular arterioles will tend to restrict renal blood flow. The effect on the efferent arteriolar resistance is, however, markedly greater, in part due to its smaller basal diameter; this tends to increase glomerular capillary hydrostatic pressure and maintain glomerular filtration rate. A number of other mechanisms can affect renal blood flow and GFR. High concentrations of Angiotensin II can constrict the glomerular mesangium, reducing the area for glomerular filtration. Angiotensin II is a sensitizer to tubuloglomerular feedback, preventing an excessive rise in GFR. Angiotensin II causes the local release of prostaglandins, which, in turn, antagonize renal vasoconstriction. The net effect of these competing mechanisms on glomerular filtration will vary with the physiological and pharmacological environment. Angiotensin was independently isolated in Indianapolis and Argentina in the late 1930s (as 'angiotonin' and 'hypertensin', respectively) and subsequently characterised and synthesized by groups at the Cleveland Clinic and Ciba laboratories in Basel, Switzerland.