1. Labelled serum protein appeared in the blood of normal and Morris hepatoma 5123 TC bearing rats 14 to 15 min after intracaval injection of radioactive leucine. Within this time albumin synthesis can be studied separately in vivo in liver and hepatomas. .Tumor bearing rats were killed within I 0 to 14 min after injection of [3H] or [14C]leucine. Postmitochondrial supernatants were prepared from 1%-labelled liver and 3H-labelled tumor, treated with sodium deoxycholate and combined. Albumin was purified from the mixture. The ratio [3H]protein to [Wlprotein decreased during purification from 7 to 1.2, suggesting that the tumor synthesized less albumin compared to total protein than the liver.3. Radiochemically pure albumin was isolated from liver and tumor homogenates from rats killed within 12 to 14 min after injection of ~-[1-14C]leucine. The specific radioactivity in albumin isolated from liver was 13 times higher than in that from tumor.4. The proportion of the incorporation of ~-[ l -~~C ] l e u c i n e into albumin to that into total protein was found to be 3.3O/, for liver and 0.8O/, for hepatoma homogenates.I n hepatectomized rats we demonstrated that the Morris hepatomas 5123 TC and 9121 and the Reuber hepatoma H 35 TC secreted little or no protein into the blood [1]. Those experiments gave no explanation for the mechanism of the observed failure of secretion of serum proteins by the hepatomas. Possibly, serum proteins were synthesized, but not released by the tumor, as suggested for the hepatomas 5123 and H 35 by Essner and Novikoff [ 2 ] , who reported the accumulation of electron-dense material in cytoplasmic granules. Another explanation would be that no serum proteins a t all were made in the hepatomas.This paper gives information whether, and to what extent, the tumor 5123 TC synthesizes serum albumin. Part of the work has been published in the form of abstracts [3,4]. MATERIAL AND METHODS Animals and TumorsAnimals were inbred Buffalo rats. They were kept in air conditioned rooms of 20" with regulated lighting (light, 9 a.m.-9 p.m.; dark, 9 p.m. to 9 a.m.) [5] and fed ad libitum with Altromin R

This study was done to obtain direct in vitro evidence for the possible existence of more than one type of dopaminergic binding site in homogenates of the caudate nucleus from calf brain. Five radioligands for dopaminergic sites were tested. The inhibitions of two agonist radioligands ([3H]dopamine, [3H]apomorphine) by haloperidol, chlorpro-mazine, or piflutixol were biphasic. The inhibitions of [3H-haloperidol, [3H]spiroperidol, and [3Hldihydroergocryptine binding by dopamine and (-)-norepinephrine were also bi-phasic. Thus, both 3H-labeled agonists and 3H-labeled antagonists were possibly binding to two high-affinity sites. There are several fundamental issues as yet unresolved concerning the nature of the dopaminergic receptor sites in the brain. A major question is whether or not there exists more than one type of dopamine receptor in the brain. Compelling evidence from in vio studies (1-5) points to the existence of presynaptic receptors (or autoreceptors) in addition to the classical type of postsynaptic receptor. Cools et al. have even further subdivided (from in vivo data) the pre-and postsynaptic receptors into excitatory and inhibitory classes (6). There has not been, however, any direct evidence for such multiple brain dopamine receptors from direct radioreceptor studies in vitro (7). Hitherto, only a single high-affinity site has been described for such dopamine receptor 3H-labeled ligands as [3H]dopamine (8-14), [3H]haloperidol (7-16), [3H]apo-morphine (17), and [3H]spiperone (18, 19). Recently, however, using [3H]dihydroergocryptine to tag dopamine receptors (in the presence of excess phentolamine to preclude binding to a-adrenergic sites), we obtained direct evidence for two dopaminergic binding sites (20). Encouraged by these observations with [3H]dihydroergocryptine, we reexamined in detail the binding patterns of the other four dopaminergic 3H-labeled ligands and found the same type of evidence for at least two high-affinity dopaminergic binding sites in each case. MATERIALS AND METHODS Preparation of Calf Caudate Nucleus Homogenates. The experiments were done on crude homogenates of calf caudate nucleus, prepared as previously described (16). In order to retain all the dopamine receptors, the homogenates were not purified or subfractionated. Calf brains were obtained fresh from the Canada Packers Hunnisett plant (Toronto). The caudates were removed within 2 hr after death, pooled, sliced into small cubes, and suspended in buffer at an approximate concentration of 50 mg of wet weight per ml of buffer. The buffer contained 15 mM Tris-HCI (pH 7.4), 5 mM Na2EDTA, 1.1 mM ascorbate, and 12.5 ,uM nialamide. A preliminary crude homogenate of the suspension was made using a glass homogenizer with a Teflon piston (0. 12-0.18 mm clearance). This piston, rotating The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U. S. C. §1734 solely to indicate this fact. at 500 rpm, was passed ...

Abstract-Effectsof YM-09151-2 and five other neuroleptics (haloperidol, spiperone, chlorpromazine, sulpiride and clozapine) on the binding of [3H]-ligands to nine different receptors (a,-adrenergic, a2-adrenergic, Q-adrenergic, muscarinic, D2-dopaminergic, H1-histaminergic, 5HT,-serotonergic, 5HT2-serotonergic and opiate receptors) and on dopamine-sensitive adenylate cyclase were determined using brain membranes in the rat, guinea-pig and dog. The affinity of YM-091 51-2 for D2-receptors with a K, value of 0.1 nM was more than 1000-times higher than that for the other receptors and dopamine sensitive adenylate cyclase, and it was the greatest among the nueroleptics tested.A close relationship between antidopami nergic and antischizophrenic effects of neu roleptics has been demonstrated by phar macological, electrophysiological, histo chemical and biochemical studies (1). Recent studies have also shown multiplicity of the dopaminergic receptors, referred to as D, (adenylate cyclase-linked), D2 (non adenylate cyclase-linked), D3 (non-adenylate cyclase-linked) and D4 (inversely adenylate cyclase-linked) according to the terminology proposed by Seeman (1, 2), in the brain; and the antischizophrenic effect seems to be at least partly attributable to a blockade of a particular type (D2) of the dopaminergic receptors. However, usefulness of the drugs in the treatment of schizophrenic patients is often limited, partly due to insufficient specificity in the affinity for the D2 dopaminergic receptors, which occasionally results in undesirable side effects such as orthostatic hypotension and thirst. Lack of specificity of neuroleptics for the D2-receptor also makes it difficult to attribute their dopaminergic functions to the D2-receptor.

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