6r PROCEEDINGS OF THE BIOCHEMICAL SOCIETY majority also contain small areas of calcium in urine may actively bind Ca2+ to form a nidus phosphate, which are not readily detectable by (Boyce, Garvey & Norfleet, 1955). However, there existing techniques such as X-ray crystallography. is little experimental evidence to support this The morphological appearance of these deposits hypothesis (Keutel, King & Boyce, 1964), and it suggests that deposition of calcium phosphate may seems likely that the organic matrix of calculi is often precede the deposition of calcium oxalate. adventitious, its presence being due to the co- These data permit a rational hypothesis for the precipitation of protein with calcium salts cause of calcium stones. The first prerequisite is (Vermeulen, Lyon & Fried, 1965). almost certainly hypercalciuria, which is generally We thank Dr R. Marshall for the data on diurnal vari- due to an increased intestinal absorption of calcium ations in urine activity products, Mr A. Chambers for the (Peacock, Hodgkinson & Nordin, 1967). In the electron micro-probe analyses and Dr. June Sutor for the presence of a high calcium concentration, over- X-ray-diffraction analyses of small urinary-tract calculi. saturation of the urine and precipitation of calcium Boyce, W. H., Garvey, F. K. & Norfleet, C. M. (1955). salts is readily produced by quite small variations Am. J. Med. 19, 87. in urine oxalate (for oxalate stones) or urine pH (for Butt, A. J. (1952). J. Urol. 67, 450. phosphate stones). Doremus, R. E. (1970). J. phy8. Chem., Ithaca, 74, 1405. Although the above outline may suffice to explain Finlayson, B. & Miller, G. H. (1969). Inve8t. Urol. 6, 428. renal stone disease, other more subtle mechanisms Fleisch, H. & Bisaz, S. (1962). Am. J. Phy8iol. 203, 671. have been invoked at various times. Thus it is Francis, M. D. (1969). Calcif. Ti8sue Re8. 3, 151. frequently suggested that normal urine contains Heaton, F. W. (1967). Clinica chim. Acta, 15, 139. factors that help to keep the calcium saltsin solution. Hodgkinson, A., Peacock, M. & Nicholson, M. (1969). These include protective colloids (Butt, 1952), Invest. Urol. 6, 549. polyphosphates (Fleisch & Bisaz, 1962) and small Howard, J. E., Thomas, W. C., Barker, L. M., Smith, L. H. & Wadkins, C. L. (1967). Johns Hopkins med. peptides (Howard, Thomas, Barker, Smith & J. 120, 119. Wadkins, 1967). Although there is good evidence Keutel, H. J., King, J. S. & Boyce, W. H. (1964). Urol. that these compounds will inhibit the precipitation int. 17, 324. ofcalcium salts in vitro, their role in stone formation Lewis, A. M., Thomas, W. C. & Tomita, A. (1966). Clin. remains unproven (Maclagan & Anderson, 1958; Sci. 30, 389. Russell & Hodgkinson, 1966; Lewis, Thomas & Maclagan, N. F. & Anderson, A. J. (1958). Br. J. Urol. Tomita,1966;Robertson,Hambleton&Hodgkinson, 30,269. 1969a). Indeed, therecognition of a metastable state Pak, C. Y. C. (1969). J. clin. Invest. 48, 1914. in urine (Robertson et al. 1968) appears to obviate Peacock, M., Hodgkinson, A. & Nordin, B. E. C. (1967). the need to invoke nucleating inhibitors, although Br. med. J. 3, 469. Raaflaub, J. (1962). Hoppe-Seyler's Z. physiol. Chem. the possibility remains that these compounds inhibit 328,198. crystal growth, rather than nucleation (Francis, Robertson, W. G., Hambleton, J. & Hodgkinson, A. 1969). Unfortunately, most studies of inhibition (1969a). Clinica chim. Acta, 25, 247. have been made without precise control of the Robertson, W. G., Peacock, M. & Nordin, B. E. C. (1968). degree of saturation of urine with respect to an Clin. Sci. 34, 579. appropriate solid phase and there is a need to Robertson,W. G., Peacock, M. & Nordin, B. E. C. (1969b). re-examine this problem in terms of the state of Lancet, ii, 21. saturation of urine. Ross, J. W. (1967). Science, N.Y., 156, 1378. Crystallization frequently involves, not only Russell, R. G. G. & Hodgkinson, A. (1966). Clin. Sci. 31, nucleation and but also 51. crystal growth, crystal Schultz, F. A., Petersen, A. J., Mask, C. A. & Buck, R. P. aggregation (Van Hook, 1961; Doremus, 1970), and (1968). Science, N.Y., 162, 267. this phenomenon may play an important part in Van Hook, A. (1961). Crystallization: Theory and Practice, stone formation. For example, large octahedral p. 228. New York: Reinhold. crystals ofcalcium oxalate dihydrateandaggregates Vermeulen, C. W., Lyon, E. S. & Fried, F. A. (1965). J. ofcrystals up to 500,umin diameter were observed in Urol. 94, 176. the urine of stone-formers after an oral dose of Walser, M. (1960). Analyt. Chem. 32, 711. sodium oxalate (Robertson etal. 1969b). In contrast, control subjects given the same dose of sodium Crystallographic Studies on the Formation of oxalate showed little or no crystalluria. Whether Renal Calculi these differences were due only to the higher Ca2+ and oxalate concentrations or to a deficiency of By D. JuwE SuTop. (Department of Chemi8try, crystallization inhibitors in the stone-forming Univer8ity CoUege London, 20 Gordon Street, London urines is under investigation. W.C.1, U.K.) Finally there is the 'matrix hypothesis', which At University College London we axe studying postulates that certain macromolecular substances urinary calculus disease by crystallographic tech- PROCEEDINGS OF THE BIOCHEMICAL SOCIETY niques using X-ray diffraction to determine stone inhibitor are not so susceptible to such fluctua- composition and crystallization experiments to tions. study growth. There are several types of calculi The principle of inhibition of crystal growth by each having different major constituents and a the presence of foreign compounds or ions in the different aetiology: juvenile bladder and a few crystallizing medium suggests a possible method of kidney stones (ammonium acid urate and calcium treatment of urinary stone disease. Experiments oxalate), adult bladder stones (uric acid), adult in vitro have shown that the rate of growth of kidney and some bladder stones (calcium oxalate calcium oxalate deposits can be retarded by many and phosphates and, in certain countries, uric acid) substances in particular those that form soluble (Lonsdale, Sutor & Wooley, 1968a,b; Sutor & stable complexes with the Ca2+ or oxalate ion and Wooley, 1969, 1970b). The geographical and those that are absorbed on to crystal faces and so historical distributions of these groups are quite prevent further growth (Sutor, 1969; Sutor & different, but there is evidence of a recurrent Wooley, 1970a). Tests on urines collected before historical pattern of change in the type and com- arLd after administration ofone ofthese compounds position of stones as a country becomes technically (Methylene Blue) to habitual formers of calcium developed. The emphasis changes from endemic oxalate stones showed the dye usually prevented bladder stones in children to kidney stones in crystalluria, slowed down nucleation in the urine adults (Andersen, 1968). The endemic stones found and substantially decreased the rate at which in this country and Europe years ago are common crystalline deposits already present grew (Sutor, today in poorer parts of developing countries like 1970). India and Thailand. With improved standards of Andersen, D. A. (1968). Ho8p. Med. 2, 1024. living the disease dies out. In the industrialized Howard, J. E. & Thomas, W. C., jun. (1958). Tran. countries adult kidney stones are the most common Am. clin. dim. A88. 70,94. type and are on the increase. They consist pre- Lonsdale, K., Sutor, D. J. & Wooley, S. E. (1968a). Br. J. dominantly of calcium oxalate and/or calcium Urol. 40, 33. phosphate and sometimes struvite (MgNH4PO4,- Lonsdale, K., Sutor, D. J. & Wooley, S. E. (1968b). Br. J. 6H20) if the urine becomes infected. In parts of Urol. 40, 402. Europe and the Middle East, uric acid is also a Sutor, D. J. (1969). Br. J. Urol. 41, 171. major constituent (Lonsdale et al. 1968b; Sutor & Sutor, D. J. (1970). Br. J. Urol. 42, 389. Wooley, 1970b). The important constituent of Sutor, D. J. & Wooley, S. E. (1969). Br. J. Urol. 41, 397. endemic stones, ammonium acid urate, is rarely Sutor, D. J. & Wooley, S. E. (1970a). Br. J. Urol. 42,296. Sutor, D. J. & Wooley, S. E. (1970b). Br. J. Urol. 42, 302. found in these calculi. Thomas, W. C., jun. (1969). In Renal Stone Besearch Urinary calculi consist predominantly of crystal- Symposium, Chapter 15, p. 141. Ed. by Hodgkinson, line material, and for nucleation and growth to A. & Nordin, B. E. C. London: J. and A. Churchill Ltd. occur, urine must be saturated or supersaturated. As many highly saturated urines never form stones, it is thought that the presence or absence of in- hibitors ofcrystallization (substances which prevent Primary Hyperoxaluria or slow down crystal growth) may explain the By R. W. E. WATTS. (Medica Research Council difference between stone-formers' and non-stone- Clinical Re8earch Centre, Watford Road, Harrow formers' urines. Experimental evidence on the HA1 3UJ, U.K.) ability of different urines to deposit apatite crystals in various mineralizing systems in vitro shows a Patients with primary hyperoxaluria present basic difference between urines from non-stone- with calcium oxalate urinary stones and are found formers and recurrent calcium-stone-formers and to have an abnormally high urinary excretion of suggests the presence of an inhibitor of calcification oxalate. The stone formation usually begins in in the urine from non-stone-formers (Howard & childhood and the victims die in early life because Thomas, 1958; Thomas, 1969). Studies on the their kidneys are destroyed inexorably by recurrent growth rate of calcium oxalate deposits in different urolithiasis and nephrocalcinosis. However, stone urines gradually saturated with calcium and oxalate formation begins later in a few cases. Disseminated ions indicate the presence of a powerful inhibitor of extra-renal deposits of calcium oxalate ('oxalosis') calcium oxalate crystal growth in urines from non- are found at autopsy; these are particularly stone-formers, which is absent or present in smaller prominent in the myocardium, muscular parts ofthe amounts in urines from calcium-stone-formers arterial walls and in the rete testis. Only a minority (D. J. Sutor, unpublished work). Urines lacking of patients with calcium oxalate urolithiasis have this inhibitor soon form crystalline deposits if primary hyperoxaluria, but its presence should be any factor increases the Ca2+ or oxalate ion sought in all patients who have a calcium oxalate concentration whereas urines containing the stone. The rate (mg/24h) at which normal subjects b